HTML5
(HyperText Markup Language)
Filename extension .html, .htm
Internet media type text/html
Type code TEXT
Uniform Type Identifier public.html
Developed by World Wide Web Consortium and WHATWG
Type of format Markup language
Extended from SGML
Extended to XHTML5
Open format? Yes
Website whatwg.org/html
www.w3.org/TR/html5
XHTML5Filename extension .xhtml, .xht, .xml, .html, .htm
Internet media type application/xml, application/xhtml+xml
Developed by World Wide Web Consortium and WHATWG
Type of format Markup language
Extended from XML, HTML5
Open format? Yes
Website www.whatwg.org/specs/web-apps/current-work/multipage/the-xhtml-syntax.html
HTML
HTML and HTML5
Dynamic HTML
XHTML
XHTML Basic
XHTML Mobile Profile and C-HTML
Canvas element
Character encodings
Document Object Model
Font family
HTML editor
HTML element
HTML Frames
HTML5 video
HTML scripting
Web browser engine
Quirks mode
Style sheets
Unicode and HTML
W3C and WHATWG
Web colors
Web Storage
Comparison of
document markup languages
web browsers
layout engines for
HTML
HTML5
HTML5 Canvas
HTML5 Media
Non-standard HTML
XHTML (1.1)
v · d · e
Tutorial: Simple game with HTML5 Canvas - part 3
Tutorial: Simple game with HTML5 Canvas
Part 1 - Introduction & Background
Part 2 - Character & Animation
Part 3 - Physics & Controls
Part 4 - Platforms & Collisions
Part 5 - Scrolling & Game States
Part 3a. PHYSICS
Because physics in StH is very simple, there is no need to include any Physics Engine such as Box2d. Jumping is so uncomplicated that it is possible to implement it just in few code lines.
Let's divide it into two unrelated parts - jumping and falling. When object start to jump, it has some initial velocity, deceased by gravity. It phase ends when that velocity is completely reduced and gravity starts to attract object down with increasing force. That is the second part of the jump - falling. To teach angel how to behave in such situations, let's expand player object with few more attributes:
view plainprint?
var player = new (function(){
var that = this;
that.image = new Image();
(...)
//new attributes
that.isJumping = false;
that.isFalling = false;
//state of the object described by bool variables - is it rising or falling?
that.jumpSpeed = 0;
that.fallSpeed = 0;
//each - jumping & falling should have its speed values
(...) //rest of the code
})();
Now lets introduce methods responsible for jumping. Further expanding of player object:
view plainprint?
that.jump = function() {
//initiation of the jump
if (!that.isJumping && !that.isFalling) {
//if objects isn't currently jumping or falling (preventing of 'double jumps', or bouncing from the air
that.fallSpeed = 0;
that.isJumping = true;
that.jumpSpeed = 17;
// initial velocity
}
}
that.checkJump = function() {
//when 'jumping' action was initiated by jump() method, initiative is taken by this one.
that.setPosition(that.X, that.Y - that.jumpSpeed);
//move object by number of pixels equal to current value of 'jumpSpeed'
that.jumpSpeed--;
//and decease it (simulation of gravity)
if (that.jumpSpeed == 0) {
//start to falling, similar to jump() function
that.isJumping = false;
that.isFalling = true;
that.fallSpeed = 1;
}
}
that.checkFall = function(){
//same situation as in checkJump()
if (that.Y < height - that.height) {
//check if the object meets the bottom of the screen, if not just change the position and increase fallSpeed (simulation of gravity acceleration)...
that.setPosition(that.X, that.Y + that.fallSpeed);
that.fallSpeed++;
} else {
//..if yes - bounce
that.fallStop();
}
}
that.fallStop = function(){
//stop falling, start jumping again
that.isFalling = false;
that.fallSpeed = 0;
that.jump();
}
It's necessarily to update main loop function to redraw player's position while jumping and falling. Update GameLoop() with this code, just before drawing the character:
view plainprint?
if (player.isJumping) player.checkJump();
if (player.isFalling) player.checkFall();
I think above code is clear enough to understand. Last action we have to take with all that physics stuff is simply initiation of the first jump, right after placing player on the stage.
view plainprint?
player.setPosition(~~((width-player.width)/2), ~~((height - player.height)/2));
player.jump(); //here
Ok, it's jumping beautifully, piece of awesome pseudo-physics code. Now let's make some controls. Part 3b. CONTROLLS Main character of StH can move sideways only. It jumps automatically, up/down movement depends of platforms. User can only command angel to move left or right. One more time it could be achieved by with extension player object with additional methods.
view plainprint?
var player = new(function(){
(...)
that.moveLeft = function(){
if (that.X > 0) {
//check whether the object is inside the screen
that.setPosition(that.X - 5, that.Y);
}
}
that.moveRight = function(){
if (that.X + that.width < width) {
//check whether the object is inside the screen
that.setPosition(that.X + 5, that.Y);
}
}
(...)
})();
Now bind that functions to the mouse pointer position (angel will follow it).
view plainprint?
document.onmousemove = function(e){
if (player.X + c.offsetLeft > e.pageX) {
//if mouse is on the left side of the player.
player.moveLeft();
} else if (player.X + c.offsetLeft < e.pageX) {
//or on right?
player.moveRight();
}
}
It's everything for today. In next episode I will introduce platform drawing and collisions. As usual: [demo with jumping & controls] [source in GitHub repo]
Tutorial: Simple game with HTML5 Canvas
Part 1 - Introduction & Background
Part 2 - Character & Animation
Part 3 - Physics & Controls
Part 4 - Platforms & Collisions
Part 5 - Scrolling & Game States
HTML5 is a language for structuring and presenting content for the World Wide Web, and is a core technology of the Internet originally proposed by Opera Software.[1] It is the fifth revision of the HTML standard (created in 1990 and standardized as HTML4 as of 1997)[2] and as of December 2011 is still under development. Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers, etc.). HTML5 is intended to subsume not only HTML 4, but XHTML 1 and DOM2HTML (particularly JavaScript) as well.[2]
Following its immediate predecessors HTML 4.01 and XHTML 1.1, HTML5 is a response to the observation that the HTML and XHTML in common use on the World Wide Web are a mixture of features introduced by various specifications, along with those introduced by software products such as web browsers, those established by common practice, and the many syntax errors in existing web documents. It is also an attempt to define a single markup language that can be written in either HTML or XHTML syntax. It includes detailed processing models to encourage more interoperable implementations; it extends, improves and rationalises the markup available for documents, and introduces markup and application programming interfaces (APIs) for complex web applications.[3] For the same reasons, HTML5 is also a potential candidate for cross-platform mobile applications. Many features of HTML5 have been built with the consideration of being able to run on low-powered devices such as smartphones and tablets. In December 2011 research firm Strategy Analytics forecast sales of HTML5 compatible phones will top 1 billion in 2013.[4]
In particular, HTML5 adds many new syntactical features. These include the <video>, <audio>, <header> and <canvas> elements, as well as the integration of SVG content that replaces the uses of generic <object> tags. These features are designed to make it easy to include and handle multimedia and graphical content on the web without having to resort to proprietary plugins and APIs. Other new elements, such as <section>, <article>, <header> and <nav>, are designed to enrich the semantic content of documents. New attributes have been introduced for the same purpose, while some elements and attributes have been removed. Some elements, such as <a>, <cite> and <menu> have been changed, redefined or standardized. The APIs and document object model (DOM) are no longer afterthoughts, but are fundamental parts of the HTML5 specification.[3] HTML5 also defines in some detail the required processing for invalid documents so that syntax errors will be treated uniformly by all conforming browsers and other user agents.[5]Contents [hide]
1 History
2 W3C standardization process
2.1 Markup
2.2 New APIs
2.3 XHTML5
2.4 Error handling
3 Popularity
4 Differences from HTML 4.01 and XHTML 1.x
5 The HTML5 logo
6 See also
7 References
8 Further reading
9 External links
[edit]
History
The Web Hypertext Application Technology Working Group (WHATWG) began work on the new standard in 2004, when the World Wide Web Consortium (W3C) was focusing future developments on XHTML 2.0, and HTML 4.01 had not been updated since 2000.[6] In 2009, the W3C allowed the XHTML 2.0 Working Group's charter to expire and decided not to renew it. W3C and WHATWG are currently working together on the development of HTML5.[7]
Even though HTML5 has been well known among web developers for years, it became the topic of mainstream media in April 2010[8][9][10][11] after Apple Inc's then-CEO Steve Jobs issued a public letter titled "Thoughts on Flash" where he concludes that Adobe "Flash is no longer necessary to watch video or consume any kind of web content" and that "new open standards created in the mobile era, such as HTML5, will win".[12] This sparked a debate in web development circles where some suggested that while HTML5 provides enhanced functionality, developers must consider the varying browser support of the different parts of the standard as well as other functionality differences between HTML5 and Flash.[13] In early November 2011 Adobe announced that it will discontinue development of Flash for mobile devices and reorient its efforts in developing tools utilizing HTML 5.[14]
[edit]
W3C standardization process
WHATWG started work on the specification in June 2004 under the name Web Applications 1.0.[15] As of January 2011, the specification is in the Draft Standard state at the WHATWG, and in Working Draft state at the W3C. Ian Hickson of Google is the editor of HTML5.[16]
The HTML5 specification was adopted as the starting point of the work of the new HTML working group of the World Wide Web Consortium (W3C) in 2007. This working group published the First Public Working Draft of the specification on 22 January 2008.[17] The specification is an ongoing work, and is expected to remain so for many years, although parts of HTML5 are going to be finished and implemented in browsers before the whole specification reaches final Recommendation status.[18]
According to the W3C timetable, it was estimated that HTML5 would reach W3C Recommendation by late 2010. However, the First Public Working Draft estimate was missed by eight months, and Last Call and Candidate Recommendation were expected to be reached in 2008,[19] but as of January 2011 HTML5 was still at Working Draft stage in the W3C.[20] HTML5 has been at Last Call in the WHATWG since October 2009.[21][22]
Ian Hickson, editor of the HTML5 specification, expects the specification to reach the Candidate Recommendation stage during 2012.[23] The criterion for the specification becoming a W3C Recommendation is "two 100% complete and fully interoperable implementations".[23] In an interview with TechRepublic, Hickson guessed that this would occur in the year 2022 or later.[24] However, many parts of the specification are stable and may be implemented in products:
Some sections are already relatively stable and there are implementations that are already quite close to completion, and those features can be used today (e.g. <canvas>).
— WHAT Working Group, When will HTML5 be finished?[23], FAQ
In December 2009, WHATWG switched to an unversioned development model for the HTML5 specification.[25] W3C will still continue with publishing a snapshot of the HTML5 specification.[26]
On 14 February 2011, the W3C extended the charter of its HTML Working Group with clear milestones for HTML5. The Working Group is expected to advance HTML5 to "Last Call", an invitation to communities inside and outside W3C to confirm the technical soundness of the specification, in May 2011. The group will then shift focus to gathering implementation experience. W3C is also developing a comprehensive test suite to achieve broad interoperability for the full specification by 2014, which is now the target date for Recommendation.[27]
Even as innovation continues, advancing HTML5 to Recommendation provides the entire Web ecosystem with a stable, tested, interoperable standard. The decision to schedule the HTML5 Last Call for May 2011 was an important step in setting industry expectations. Today we take the next step, announcing 2014 as the target for Recommendation.
— Jeff Jaffe, Chief Executive Officer, World Wide Web Consortium[27]
[edit]
Markup
HTML5 introduces a number of new elements and attributes that reflect typical usage on modern websites. Some of them are semantic replacements for common uses of generic block (<div>) and inline (<span>) elements, for example <nav> (website navigation block), <footer> (usually referring to bottom of web page or to last lines of HTML code), or <audio> and <video> instead of <object>.[28][29][30] Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as <font> and <center>, whose effects are achieved using Cascading Style Sheets. There is also a renewed emphasis on the importance of DOM scripting (e.g., JavaScript) in Web behavior.
The HTML5 syntax is no longer based on SGML[dubious – discuss] despite the similarity of its markup. It has, however, been designed to be backward compatible with common parsing of older versions of HTML. It comes with a new introductory line that looks like an SGML document type declaration, <!DOCTYPE html>, which triggers the standards-compliant rendering mode.[31] As of 5 January 2009, HTML5 also includes Web Forms 2.0, a previously separate WHATWG specification.
[edit]
New APIs
In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs).[32] Existing document object model (DOM) interfaces are extended and de facto features documented. There are also new APIs, such as:The canvas element for immediate mode 2D drawing. See Canvas 2D API Specification 1.0 specification[33]
Timed media playback
Offline Web Applications[34]
Document editing Drag-and-drop
Cross-document messaging[35]
Browser history management
MIME type and protocol handler registration
Microdata
Not all of the above technologies are included in the W3C HTML5 specification, though they are in the WHATWG HTML specification.[36] Some related technologies, which are not part of either the W3C HTML5 or the WHATWG HTML specification, are as follows. The W3C publishes specifications for these separately.Geolocation
Web SQL Database, a local SQL Database (no longer maintained).[37]
The Indexed Database API, an indexed hierarchical key-value store (formerly WebSimpleDB).[38]
Web Storage, a key-value pair storage framework that provides enhanced behaviour similar to Cookies but with larger storage capacity and improved API.[39] File API, Handle file uploads and file manipulation.[40]
Directories and System. This API is intended to satisfy client-side-storage use cases not well served by databases.[41]
File Writer. An API for writing to files from web applications.[42]
A common misconception is that HTML5 can provide animation within web pages, which is untrue. Either JavaScript or CSS3 is necessary for animating HTML elements. Animation is also possible using JavaScript and HTML 4[43][not in citation given], and within SVG elements through SMIL, although browser support of the latter remains uneven as of 2011.
[edit]
XHTML5
XHTML5 is the XML serialization of HTML5. XML documents must be served with an XML Internet media type such as application/xhtml+xml or application/xml.[44] XHTML5 requires XML's strict, well-formed syntax. The choice between HTML5 and XHTML5 boils down to the choice of a MIME/content type: the media type one chooses determines what type of document should be used.[45] In XHTML5 the HTML5 doctype html is optional and may simply be omitted.[46] HTML that has been written to conform to both the HTML and XHTML specifications—and which will therefore produce the same DOM tree whether parsed as HTML or XML—is termed "polyglot markup".[47]
[edit]
Error handling
An HTML5 (text/html) browser will be flexible in handling incorrect syntax. HTML5 is designed so that old browsers can safely ignore new HTML5 constructs. In contrast to HTML 4.01, the HTML5 specification gives detailed rules for lexing and parsing, with the intent that different compliant browsers will produce the same result in the case of incorrect syntax.[48] Although HTML5 now defines a consistent behavior for "tag soup" documents, those documents are not regarded as conforming to the HTML5 standard.[48]
[edit]
Popularity
According to a report released on 30 September 2011, 34 of the world's top 100 Web sites were using HTML5 – the adaptation led by search engines and social networks.[49]
[edit]
Differences from HTML 4.01 and XHTML 1.x
The following is a cursory list of differences and some specific examples.New parsing rules: oriented towards flexible parsing and compatibility; not based on SGML
Ability to use inline SVG and MathML in text/html
New elements: article, aside, audio, bdo, canvas, command, datalist, details, embed, figcaption, figure, footer, header, hgroup, keygen, mark, meter, nav, output, progress, rp, rt, ruby, section, source, summary, time, video, wbr New types of form controls: dates and times, email, url, search, number, range, tel, color[50]
New attributes: charset (on meta), async (on script)
Global attributes (that can be applied for every element): id, tabindex, hidden, data-* (custom data attributes)
Deprecated elements will be dropped altogether: acronym, applet, basefont, big, center, dir, font, frame, frameset, isindex, noframes, strike, tt
dev.w3.org provides the latest Editors Draft (last dated 4 August 2011) of "HTML5 differences from HTML4",[51] which provides a complete outline of additions, removals and changes between HTML5 and HTML4.
[edit]
The HTML5 logo
The W3C HTML5 logo
On 18 January 2011, the W3C introduced a logo to represent the use of or interest in HTML5. Unlike other badges previously issued by the W3C, it does not imply validity or conformance to a certain standard. As of 1 April 2011, this logo is official.[52]
When initially presenting it to the public, the W3C announced the HTML5 logo as a "general-purpose visual identity for a broad set of open web technologies, including HTML5, CSS, SVG, WOFF, and others".[53] Some web standard advocates, including The Web Standards Project, criticised that definition of "HTML5" as an umbrella term, pointing out the blurring of terminology and the potential for miscommunication.[53] Three days later, the W3C responded to community feedback and changed the logo's definition, dropping the enumeration of related technologies.[54] The W3C then said the logo "represents HTML5, the cornerstone for modern Web applications".[52]
HyperText Markup Language (HTML) is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages.
HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content. HTML tags most commonly come in pairs like <h1> and </h1>, although some tags, known as empty elements, are unpaired, for example <img>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags). In between these tags web designers can add text, tags, comments and other types of text-based content.
The purpose of a web browser is to read HTML documents and compose them into visible or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.
HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It can embed scripts in languages such as JavaScript which affect the behavior of HTML webpages.
Web browsers can also refer to Cascading Style Sheets (CSS) to define the appearance and layout of text and other material. The W3C, maintainer of both the HTML and the CSS standards, encourages the use of CSS over explicitly presentational HTML markup.[1]Contents [hide]
1 History
1.1 Origins
1.2 First specifications
1.3 Version history of the standard
1.3.1 HTML version timeline
1.3.2 HTML draft version timeline
1.3.3 XHTML versions
2 Markup
2.1 Elements
2.1.1 Element examples
2.1.2 Attributes
2.2 Character and entity references
2.3 Data types
2.4 Document type declaration
3 Semantic HTML
4 Delivery
4.1 HTTP
4.2 HTML e-mail
4.3 Naming conventions
4.4 HTML Application
5 Current variations
5.1 SGML-based versus XML-based HTML
5.2 Transitional versus strict
5.3 Frameset versus transitional
5.4 Summary of specification versions
6 Hypertext features not in HTML
7 WYSIWYG editors
8 See also
9 References
10 External links
[edit]
History
[edit]
Origins
Tim Berners-Lee
In 1980, physicist Tim Berners-Lee, who was a contractor at CERN, proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents. In 1989, Berners-Lee wrote a memo proposing an Internet-based hypertext system.[2] Berners-Lee specified HTML and wrote the browser and server software in the last part of 1990. In that year, Berners-Lee and CERN data systems engineer Robert Cailliau collaborated on a joint request for funding, but the project was not formally adopted by CERN. In his personal notes[3] from 1990 he lists[4] "some of the many areas in which hypertext is used" and puts an encyclopedia first.
[edit]
First specifications
The first publicly available description of HTML was a document called "HTML Tags", first mentioned on the Internet by Berners-Lee in late 1991.[5][6] It describes 20 elements comprising the initial, relatively simple design of HTML. Except for the hyperlink tag, these were strongly influenced by SGMLguid, an in-house SGML based documentation format at CERN. Thirteen of these elements still exist in HTML 4.[7]
Hypertext markup language is a markup language that web browsers use to interpret and compose text, images and other material into visual or audible web pages. Default characteristics for every item of HTML markup are defined in the browser, and these characteristics can be altered or enhanced by the web page designer's additional use of CSS. Many of the text elements are found in the 1988 ISO technical report TR 9537 Techniques for using SGML, which in turn covers the features of early text formatting languages such as that used by the RUNOFF command developed in the early 1960s for the CTSS (Compatible Time-Sharing System) operating system: these formatting commands were derived from the commands used by typesetters to manually format documents. However, the SGML concept of generalized markup is based on elements (nested annotated ranges with attributes) rather than merely print effects, with also the separation of structure and processing; HTML has been progressively moved in this direction with CSS.
Berners-Lee considered HTML to be an application of SGML. It was formally defined as such by the Internet Engineering Task Force (IETF) with the mid-1993 publication of the first proposal for an HTML specification: "Hypertext Markup Language (HTML)" Internet-Draft by Berners-Lee and Dan Connolly, which included an SGML Document Type Definition to define the grammar.[8] The draft expired after six months, but was notable for its acknowledgement of the NCSA Mosaic browser's custom tag for embedding in-line images, reflecting the IETF's philosophy of basing standards on successful prototypes.[9] Similarly, Dave Raggett's competing Internet-Draft, "HTML+ (Hypertext Markup Format)", from late 1993, suggested standardizing already-implemented features like tables and fill-out forms.[10]
After the HTML and HTML+ drafts expired in early 1994, the IETF created an HTML Working Group, which in 1995 completed "HTML 2.0", the first HTML specification intended to be treated as a standard against which future implementations should be based.[9] Published as Request for Comments 1866, HTML 2.0 included ideas from the HTML and HTML+ drafts.[11] The 2.0 designation was intended to distinguish the new edition from previous drafts.[12]
Further development under the auspices of the IETF was stalled by competing interests. Since 1996, the HTML specifications have been maintained, with input from commercial software vendors, by the World Wide Web Consortium (W3C).[13] However, in 2000, HTML also became an international standard (ISO/IEC 15445:2000). The last HTML specification published by the W3C is the HTML 4.01 Recommendation, published in late 1999. Its issues and errors were last acknowledged by errata published in 2001.
[edit]
Version history of the standardHTML
HTML and HTML5
Dynamic HTML
XHTML
XHTML Basic
XHTML Mobile Profile and C-HTML
Canvas element
Character encodings
Document Object Model
Font family
HTML editor
HTML element
HTML Frames
HTML5 video
HTML scripting
Web browser engine
Quirks mode
Style sheets
Unicode and HTML
W3C and WHATWG
Web colors
Web Storage
Comparison of
document markup languages
web browsers
layout engines for
HTML
HTML5
HTML5 Canvas
HTML5 Media
Non-standard HTML
XHTML (1.1)
v · d · e
[edit]
HTML version timeline
November 24, 1995
HTML 2.0 was published as IETF RFC 1866. Supplemental RFCs added capabilities:
November 25, 1995: RFC 1867 (form-based file upload)
May 1996: RFC 1942 (tables)
August 1996: RFC 1980 (client-side image maps)
January 1997: RFC 2070 (internationalization)
January 1997
HTML 3.2[14] was published as a W3C Recommendation. It was the first version developed and standardized exclusively by the W3C, as the IETF had closed its HTML Working Group in September 1996.[15]
HTML 3.2 dropped math formulas entirely, reconciled overlap among various proprietary extensions and adopted most of Netscape's visual markup tags. Netscape's blink element and Microsoft's marquee element were omitted due to a mutual agreement between the two companies.[13] A markup for mathematical formulas similar to that in HTML was not standardized until 14 months later in MathML.
December 1997
HTML 4.0[16] was published as a W3C Recommendation. It offers three variations:
Strict, in which deprecated elements are forbidden,
Transitional, in which deprecated elements are allowed,
Frameset, in which mostly only frame related elements are allowed;
Initially code-named "Cougar",[17] HTML 4.0 adopted many browser-specific element types and attributes, but at the same time sought to phase out Netscape's visual markup features by marking them as deprecated in favor of style sheets. HTML 4 is an SGML application conforming to ISO 8879 - SGML.[18]
April 1998
HTML 4.0[19] was reissued with minor edits without incrementing the version number.
December 1999
HTML 4.01[20] was published as a W3C Recommendation. It offers the same three variations as HTML 4.0 and its last errata were published May 12, 2001.
May 2000
ISO/IEC 15445:2000[21][22] ("ISO HTML", based on HTML 4.01 Strict) was published as an ISO/IEC international standard. In the ISO this standard falls in the domain of the ISO/IEC JTC1/SC34 (ISO/IEC Joint Technical Committee 1, Subcommittee 34 - Document description and processing languages).ajmal[21]
As of mid-2008, HTML 4.01 and ISO/IEC 15445:2000 are the most recent versions of HTML. Development of the parallel, XML-based language XHTML occupied the W3C's HTML Working Group through the early and mid-2000s.
[edit]
HTML draft version timeline
Logo of HTML 5
October 1991
HTML Tags,[5] an informal CERN document listing twelve HTML tags, was first mentioned in public.
June 1992
First informal draft of the HTML DTD,[23] with seven[24][25][26] subsequent revisions (July 15, August 6, August 18, November 17, November 19, November 20, November 22)
November 1992
HTML DTD 1.1 (the first with a version number, based on RCS revisions, which start with 1.1 rather than 1.0), an informal draft[26]
June 1993
Hypertext Markup Language[27] was published by the IETF IIIR Working Group as an Internet-Draft (a rough proposal for a standard). It was replaced by a second version[28] one month later, followed by six further drafts published by IETF itself[29] that finally led to HTML 2.0 in RFC1866
November 1993
HTML+ was published by the IETF as an Internet-Draft and was a competing proposal to the Hypertext Markup Language draft. It expired in May 1994.
April 1995 (authored March 1995)
HTML 3.0[30] was proposed as a standard to the IETF, but the proposal expired five months later without further action. It included many of the capabilities that were in Raggett's HTML+ proposal, such as support for tables, text flow around figures and the display of complex mathematical formulas.[31]
W3C began development of its own Arena browser as a test bed for HTML 3 and Cascading Style Sheets,[32][33][34] but HTML 3.0 did not succeed for several reasons. The draft was considered very large at 150 pages and the pace of browser development, as well as the number of interested parties, had outstripped the resources of the IETF.[13] Browser vendors, including Microsoft and Netscape at the time, chose to implement different subsets of HTML 3's draft features as well as to introduce their own extensions to it.[13] (See Browser wars) These included extensions to control stylistic aspects of documents, contrary to the "belief [of the academic engineering community] that such things as text color, background texture, font size and font face were definitely outside the scope of a language when their only intent was to specify how a document would be organized."[13] Dave Raggett, who has been a W3C Fellow for many years has commented for example, "To a certain extent, Microsoft built its business on the Web by extending HTML features."[13]
January 2008
HTML5 was published as a Working Draft (link) by the W3C.[35]
Although its syntax closely resembles that of SGML, HTML5 has abandoned any attempt to be an SGML application and has explicitly defined its own "html" serialization, in addition to an alternative XML-based XHTML5 serialization.[36]
[edit]
XHTML versions
Main article: XHTML
XHTML is a separate language that began as a reformulation of HTML 4.01 using XML 1.0. It continues to be developed:
XHTML 1.0,[37] published January 26, 2000, as a W3C Recommendation, later revised and republished August 1, 2002. It offers the same three variations as HTML 4.0 and 4.01, reformulated in XML, with minor restrictions.
XHTML 1.1,[38] published May 31, 2001, as a W3C Recommendation. It is based on XHTML 1.0 Strict, but includes minor changes, can be customized, is reformulated using modules from Modularization of XHTML, which was published April 10, 2001, as a W3C Recommendation.
XHTML 2.0,.[39][40] There is no XHTML 2.0 standard. XHTML 2.0 is only a draft document and it is inappropriate to cite this document as other than work in progress. XHTML 2.0 is incompatible with XHTML 1.x and, therefore, would be more accurately characterized as an XHTML-inspired new language than an update to XHTML 1.x.
XHTML5, which is an update to XHTML 1.x, is being defined alongside HTML5 in the HTML5 draft.[41]
[edit]
Markup
HTML markup consists of several key components, including elements (and their attributes), character-based data types, character references and entity references. Another important component is the document type declaration, which triggers standards mode rendering.
The Hello world program, a common computer program employed for comparing programming languages, scripting languages and markup languages is made of 9 lines of code, although in HTML newlines are optional:
<!DOCTYPE html>
<html>
<head>
<title>Hello HTML</title>
</head>
<body>
<p>Hello World!</p>
</body>
</html>
(The text between <html> and </html> describes the web page, and the text between <body> and </body> is the visible page content. The markup text '<title>Hello HTML</title>' defines the browser tab title.)
This Document Type Declaration is for HTML5. If the <!doctype html> declaration is not included, various browsers will revert to "quirks mode" for rendering.[42]
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Elements
Main article: HTML element
HTML documents are composed entirely of HTML elements that, in their most general form have three components: a pair of tags, a "start tag" and "end tag"; some attributes within the start tag; and finally, any textual and graphical content between the start and end tags, perhaps including other nested elements. The HTML element is everything between and including the start and end tags. Each tag is enclosed in angle brackets.
The general form of an HTML element is therefore: <tag attribute1="value1" attribute2="value2">content</tag>. Some HTML elements are defined as empty elements and take the form <tag attribute1="value1" attribute2="value2" >. Empty elements may enclose no content, for instance, the BR tag or the inline IMG tag. The name of an HTML element is the name used in the tags. Note that the end tag's name is preceded by a slash character, "/", and that in empty elements the end tag is neither required nor allowed. If attributes are not mentioned, default values are used in each case.
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Element examples
Header of the HTML document:<head>...</head>. Usually the title should be included in the head, for example:
<head>
<title>The title</title>
</head>
Headings: HTML headings are defined with the <h1> to <h6> tags:
<h1>Heading1</h1>
<h2>Heading2</h2>
<h3>Heading3</h3>
<h4>Heading4</h4>
<h5>Heading5</h5>
<h6>Heading6</h6>
Paragraphs:
<p>Paragraph 1</p> <p>Paragraph 2</p>
Line breaks:<br>. The difference between <br> and <p> is that 'br' breaks a line without altering the semantic structure of the page, whereas 'p' sections the page into paragraphs. Note also that 'br' is an empty element in that, while it may have attributes, it can take no content and it may not have an end tag.
<p>This <br> is a paragraph <br> with <br> line breaks</p>
Comments:
<!-- This is a comment -->
Comments can help understanding of the markup and do not display in the webpage.
There are several types of markup elements used in HTML.
Structural markup describes the purpose of text
For example, <h2>Golf</h2> establishes "Golf" as a second-level heading. Structural markup does not denote any specific rendering, but most web browsers have default styles for element formatting. Content may be further styled using Cascading Style Sheets (CSS).
Presentational markup describes the appearance of the text, regardless of its purpose
For example <b>boldface</b> indicates that visual output devices should render "boldface" in bold text, but gives little indication what devices that are unable to do this (such as aural devices that read the text aloud) should do. In the case of both <b>bold</b> and <i>italic</i>, there are other elements that may have equivalent visual renderings but which are more semantic in nature, such as <strong>strong text</strong> and <em>emphasised text</em> respectively. It is easier to see how an aural user agent should interpret the latter two elements. However, they are not equivalent to their presentational counterparts: it would be undesirable for a screen-reader to emphasize the name of a book, for instance, but on a screen such a name would be italicized. Most presentational markup elements have become deprecated under the HTML 4.0 specification, in favor of using CSS for styling.
Hypertext markup makes parts of a document into links to other documents
An anchor element creates a hyperlink in the document and its href attribute sets the link's target URL. For example the HTML markup, <a href="http://www.google.com/">Wikipedia</a>, will render the word "Wikipedia" as a hyperlink. To render an image as a hyperlink, an 'img' element is inserted as content into the 'a' element. Like 'br', 'img' is an empty element with attributes but no content or closing tag. <a href="http://example.org"><img src="image.gif" alt="descriptive text" width="50" height="50" border="0"></a>.
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Attributes
Most of the attributes of an element are name-value pairs, separated by "=" and written within the start tag of an element after the element's name. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but not XHTML).[43][44] Leaving attribute values unquoted is considered unsafe.[45] In contrast with name-value pair attributes, there are some attributes that affect the element simply by their presence in the start tag of the element,[5] like the ismap attribute for the img element.[46]
There are several common attributes that may appear in many elements:
The id attribute provides a document-wide unique identifier for an element. This is used to identify the element so that stylesheets can alter its presentational properties, and scripts may alter, animate or delete its contents or presentation. Appended to the URL of the page, it provides a globally unique identifier for the element, typically a sub-section of the page. For example, the ID "Attributes" in http://en.wikipedia.org/wiki/HTML#Attributes
The class attribute provides a way of classifying similar elements. This can be used for semantic or presentation purposes. For example, an HTML document might semantically use the designation class="notation" to indicate that all elements with this class value are subordinate to the main text of the document. In presentation, such elements might be gathered together and presented as footnotes on a page instead of appearing in the place where they occur in the HTML source. Class attributes are used semantically in microformats. Multiple class values may be specified; for example class="notation important" puts the element into both the 'notation' and the 'important' classes.
An author may use the style attribute to assign presentational properties to a particular element. It is considered better practice to use an element's id or class attributes to select the element from within a stylesheet, though sometimes this can be too cumbersome for a simple, specific, or ad hoc styling.
The title attribute is used to attach subtextual explanation to an element. In most browsers this attribute is displayed as a tooltip.
The lang attribute identifies the natural language of the element's contents, which may be different from that of the rest of the document. For example, in an English-language document:
<p>Oh well, <span lang="fr">c'est la vie</span>, as they say in France.</p>
The abbreviation element, abbr, can be used to demonstrate some of these attributes:
<abbr id="anId" class="jargon" style="color:purple;" title="Hypertext Markup Language">HTML</abbr>
This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language."
Most elements also take the language-related attribute dir to specify text direction, such as with "rtl" for right-to-left text in, for example, Arabic, Persian or Hebrew.[47]
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Character and entity references
See also: List of XML and HTML character entity references and Unicode and HTML
As of version 4.0, HTML defines a set of 252 character entity references and a set of 1,114,050 numeric character references, both of which allow individual characters to be written via simple markup, rather than literally. A literal character and its markup counterpart are considered equivalent and are rendered identically.
The ability to "escape" characters in this way allows for the characters < and & (when written as < and &, respectively) to be interpreted as character data, rather than markup. For example, a literal < normally indicates the start of a tag, and & normally indicates the start of a character entity reference or numeric character reference; writing it as & or & or & allows & to be included in the content of an element or in the value of an attribute. The double-quote character ("), when not used to quote an attribute value, must also be escaped as " or " or " when it appears within the attribute value itself. Equivalently, the single-quote character ('), when used to quote an attribute value, must also be escaped as ' or ' (not as ' except in XHTML documents[48]) when it appears within the attribute value itself. If document authors overlook the need to escape such characters, some browsers can be very forgiving and try to use context to guess their intent. The result is still invalid markup, which makes the document less accessible to other browsers and to other user agents that may try to parse the document for search and indexing purposes for example.
Escaping also allows for characters that are not easily typed, or that are not available in the document's character encoding, to be represented within element and attribute content. For example, the acute-accented e (é), a character typically found only on Western European keyboards, can be written in any HTML document as the entity reference é or as the numeric references é or é, using characters that are available on all keyboards and are supported in all character encodings. Unicode character encodings such as UTF-8 are compatible with all modern browsers and allow direct access to almost all the characters of the world's writing systems.[49]
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Data types
HTML defines several data types for element content, such as script data and stylesheet data, and a plethora of types for attribute values, including IDs, names, URIs, numbers, units of length, languages, media descriptors, colors, character encodings, dates and times, and so on. All of these data types are specializations of character data.
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Document type declaration
HTML documents are required to start with a Document Type Declaration (informally, a "doctype"). In browsers, the doctype helps to define the rendering mode—particularly whether to use quirks mode.
The original purpose of the doctype was to enable parsing and validation of HTML documents by SGML tools based on the Document Type Definition (DTD). The DTD to which the DOCTYPE refers contains a machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers, on the other hand, do not implement HTML as an application of SGML and by consequence do not read the DTD. HTML5 does not define a DTD, because of the technology's inherent limitations, so in HTML5 the doctype declaration, <!doctype html>, does not refer to a DTD.
An example of an HTML 4 doctype is
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
This declaration references the DTD for the 'strict' version of HTML 4.01. SGML-based validators read the DTD in order to properly parse the document and to perform validation. In modern browsers, a valid doctype activates standards mode as opposed to quirks mode.
In addition, HTML 4.01 provides Transitional and Frameset DTDs, as explained below.
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Semantic HTML
Main article: Semantic HTML
Semantic HTML is a way of writing HTML that emphasizes the meaning of the encoded information over its presentation (look). HTML has included semantic markup from its inception,[50] but has also included presentational markup such as <font>, <i> and <center> tags. There are also the semantically neutral span and div tags. Since the late 1990s when Cascading Style Sheets were beginning to work in most browsers, web authors have been encouraged to avoid the use of presentational HTML markup with a view to the separation of presentation and content.[51]
In a 2001 discussion of the Semantic Web, Tim Berners-Lee and others gave examples of ways in which intelligent software 'agents' may one day automatically trawl the Web and find, filter and correlate previously unrelated, published facts for the benefit of human users.[52] Such agents are not commonplace even now, but some of the ideas of Web 2.0, mashups and price comparison websites may be coming close. The main difference between these web application hybrids and Berners-Lee's semantic agents lies in the fact that the current aggregation and hybridisation of information is usually designed in by web developers, who already know the web locations and the API semantics of the specific data they wish to mash, compare and combine.
An important type of web agent that does trawl and read web pages automatically, without prior knowledge of what it might find, is the Web crawler or search-engine spider. These software agents are dependent on the semantic clarity of web pages they find as they use various techniques and algorithms to read and index millions of web pages a day and provide web users with search facilities without which the World Wide Web would be only a fraction of its current usefulness.
In order for search-engine spiders to be able to rate the significance of pieces of text they find in HTML documents, and also for those creating mashups and other hybrids as well as for more automated agents as they are developed, the semantic structures that exist in HTML need to be widely and uniformly applied to bring out the meaning of published text.[53]
Presentational markup tags are deprecated in current HTML and XHTML recommendations and are illegal in HTML5.
Good semantic HTML also improves the accessibility of web documents (see also Web Content Accessibility Guidelines). For example, when a screen reader or audio browser can correctly ascertain the structure of a document, it will not waste the visually impaired user's time by reading out repeated or irrelevant information when it has been marked up correctly.
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Delivery
HTML documents can be delivered by the same means as any other computer file. However, they are most often delivered either by HTTP from a web server or by email.
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HTTP
Main article: Hypertext Transfer Protocol
The World Wide Web is composed primarily of HTML documents transmitted from web servers to web browsers using the Hypertext Transfer Protocol (HTTP). However, HTTP is used to serve images, sound, and other content, in addition to HTML. To allow the Web browser to know how to handle each document it receives, other information is transmitted along with the document. This meta data usually includes the MIME type (e.g. text/html or application/xhtml+xml) and the character encoding (see Character encoding in HTML).
In modern browsers, the MIME type that is sent with the HTML document may affect how the document is initially interpreted. A document sent with the XHTML MIME type is expected to be well-formed XML; syntax errors may cause the browser to fail to render it. The same document sent with the HTML MIME type might be displayed successfully, since some browsers are more lenient with HTML.
The W3C recommendations state that XHTML 1.0 documents that follow guidelines set forth in the recommendation's Appendix C may be labeled with either MIME Type.[54] The current XHTML 1.1 Working Draft also states that XHTML 1.1 documents should[55] be labeled with either MIME type.[56]
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HTML e-mail
Main article: HTML email
Most graphical email clients allow the use of a subset of HTML (often ill-defined) to provide formatting and semantic markup not available with plain text. This may include typographic information like coloured headings, emphasized and quoted text, inline images and diagrams. Many such clients include both a GUI editor for composing HTML e-mail messages and a rendering engine for displaying them. Use of HTML in e-mail is controversial because of compatibility issues, because it can help disguise phishing attacks, because it can confuse spam filters and because the message size is larger than plain text.
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Naming conventions
The most common filename extension for files containing HTML is .html. A common abbreviation of this is .htm, which originated because some early operating systems and file systems, such as DOS and FAT, limited file extensions to three letters.
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HTML Application
Main article: HTML Application
An HTML Application (HTA; file extension ".hta") is a Microsoft Windows application that uses HTML and Dynamic HTML in a browser to provide the application's graphical interface. A regular HTML file is confined to the security model of the web browser, communicating only to web servers and manipulating only webpage objects and site cookies. An HTA runs as a fully trusted application and therefore has more privileges, like creation/editing/removal of files and Windows Registry entries. Because they operate outside the browser's security model, HTAs cannot be executed via HTTP, but must be downloaded (just like an EXE file) and executed from local file system.
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Current variations
HTML is precisely what we were trying to PREVENT— ever-breaking links, links going outward only, quotes you can't follow to their origins, no version management, no rights management.
Ted Nelson[57]
Since its inception, HTML and its associated protocols gained acceptance relatively quickly. However, no clear standards existed in the early years of the language. Though its creators originally conceived of HTML as a semantic language devoid of presentation details,[58] practical uses pushed many presentational elements and attributes into the language, driven largely by the various browser vendors. The latest standards surrounding HTML reflect efforts to overcome the sometimes chaotic development of the language[59] and to create a rational foundation for building both meaningful and well-presented documents. To return HTML to its role as a semantic language, the W3C has developed style languages such as CSS and XSL to shoulder the burden of presentation. In conjunction, the HTML specification has slowly reined in the presentational elements.
There are two axes differentiating various variations of HTML as currently specified: SGML-based HTML versus XML-based HTML (referred to as XHTML) on one axis, and strict versus transitional (loose) versus frameset on the other axis.
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SGML-based versus XML-based HTML
One difference in the latest HTML specifications lies in the distinction between the SGML-based specification and the XML-based specification. The XML-based specification is usually called XHTML to distinguish it clearly from the more traditional definition. However, the root element name continues to be 'html' even in the XHTML-specified HTML. The W3C intended XHTML 1.0 to be identical to HTML 4.01 except where limitations of XML over the more complex SGML require workarounds. Because XHTML and HTML are closely related, they are sometimes documented in parallel. In such circumstances, some authors conflate the two names as (X)HTML or X(HTML).
Like HTML 4.01, XHTML 1.0 has three sub-specifications: strict, transitional and frameset.
Aside from the different opening declarations for a document, the differences between an HTML 4.01 and XHTML 1.0 document—in each of the corresponding DTDs—are largely syntactic. The underlying syntax of HTML allows many shortcuts that XHTML does not, such as elements with optional opening or closing tags, and even EMPTY elements which must not have an end tag. By contrast, XHTML requires all elements to have an opening tag and a closing tag. XHTML, however, also introduces a new shortcut: an XHTML tag may be opened and closed within the same tag, by including a slash before the end of the tag like this: <br/>. The introduction of this shorthand, which is not used in the SGML declaration for HTML 4.01, may confuse earlier software unfamiliar with this new convention. A fix for this is to include a space before closing the tag, as such: <br />.[60]
To understand the subtle differences between HTML and XHTML, consider the transformation of a valid and well-formed XHTML 1.0 document that adheres to Appendix C (see below) into a valid HTML 4.01 document. To make this translation requires the following steps:
The language for an element should be specified with a lang attribute rather than the XHTML xml:lang attribute. XHTML uses XML's built in language-defining functionality attribute.
Remove the XML namespace (xmlns=URI). HTML has no facilities for namespaces.
Change the document type declaration from XHTML 1.0 to HTML 4.01. (see DTD section for further explanation).
If present, remove the XML declaration. (Typically this is: <?xml version="1.0" encoding="utf-8"?>).
Ensure that the document's MIME type is set to text/html. For both HTML and XHTML, this comes from the HTTP Content-Type header sent by the server.
Change the XML empty-element syntax to an HTML style empty element (<br/> to <br>).
Those are the main changes necessary to translate a document from XHTML 1.0 to HTML 4.01. To translate from HTML to XHTML would also require the addition of any omitted opening or closing tags. Whether coding in HTML or XHTML it may just be best to always include the optional tags within an HTML document rather than remembering which tags can be omitted.
A well-formed XHTML document adheres to all the syntax requirements of XML. A valid document adheres to the content specification for XHTML, which describes the document structure.
The W3C recommends several conventions to ensure an easy migration between HTML and XHTML (see HTML Compatibility Guidelines). The following steps can be applied to XHTML 1.0 documents only:
Include both xml:lang and lang attributes on any elements assigning language.
Use the empty-element syntax only for elements specified as empty in HTML.
Include an extra space in empty-element tags: for example <br /> instead of <br/>.
Include explicit close tags for elements that permit content but are left empty (for example, <div></div>, not <div />).
Omit the XML declaration.
By carefully following the W3C's compatibility guidelines, a user agent should be able to interpret the document equally as HTML or XHTML. For documents that are XHTML 1.0 and have been made compatible in this way, the W3C permits them to be served either as HTML (with a text/html MIME type), or as XHTML (with an application/xhtml+xml or application/xml MIME type). When delivered as XHTML, browsers should use an XML parser, which adheres strictly to the XML specifications for parsing the document's contents.
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Transitional versus strict
HTML 4 defined three different versions of the language: Strict, Transitional (once called Loose) and Frameset. The Strict version is intended for new documents and is considered best practice, while the Transitional and Frameset versions were developed to make it easier to transition documents that conformed to older HTML specification or didn't conform to any specification to a version of HTML 4. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version. Instead, cascading style sheets are encouraged to improve the presentation of HTML documents. Because XHTML 1 only defines an XML syntax for the language defined by HTML 4, the same differences apply to XHTML 1 as well. The Transitional version allows the following parts of the vocabulary, which are not included in the Strict version:
A looser content model
Inline elements and plain text are allowed directly in: body, blockquote, form, noscript and noframes
Presentation related elements
underline (u)(Deprecated. can confuse a visitor with a hyperlink.)
strike-through (s)
center(Deprecated. use CSS instead.)
font(Deprecated. use CSS instead.)
basefont(Deprecated. use CSS instead.)
Presentation related attributes
background(Deprecated. use CSS instead.) and bgcolor(Deprecated. use CSS instead.) attributes for body(required element according to the W3C.) element.
align(Deprecated. use CSS instead.) attribute on div, form, paragraph (p) and heading (h1...h6) elements
align(Deprecated. use CSS instead.), noshade(Deprecated. use CSS instead.), size(Deprecated. use CSS instead.) and width(Deprecated. use CSS instead.) attributes on hr element
align(Deprecated. use CSS instead.), border, vspace and hspace attributes on img and object(caution: the object element is only supported in Internet Explorer(from the major browsers)) elements
align(Deprecated. use CSS instead.) attribute on legend and caption elements
align(Deprecated. use CSS instead.) and bgcolor(Deprecated. use CSS instead.) on table element
nowrap(Obsolete), bgcolor(Deprecated. use CSS instead.), width, height on td and th elements
bgcolor(Deprecated. use CSS instead.) attribute on tr element
clear(Obsolete) attribute on br element
compact attribute on dl, dir and menu elements
type(Deprecated. use CSS instead.), compact(Deprecated. use CSS instead.) and start(Deprecated. use CSS instead.) attributes on ol and ul elements
type and value attributes on li element
width attribute on pre element
Additional elements in Transitional specification
menu(Deprecated. use CSS instead.) list (no substitute, though unordered list is recommended)
dir(Deprecated. use CSS instead.) list (no substitute, though unordered list is recommended)
isindex(Deprecated.) (element requires server-side support and is typically added to documents server-side, form and input elements can be used as a substitute)
applet (Deprecated. use the object element instead.)
The language(Obsolete) attribute on script element (redundant with the type attribute).
Frame related entities
iframe
noframes
target(Deprecated in the map, link and form elements.) attribute on a, client-side image-map (map), link, form and base elements
The Frameset version includes everything in the Transitional version, as well as the frameset element (used instead of body) and the frame element.
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Frameset versus transitional
In addition to the above transitional differences, the frameset specifications (whether XHTML 1.0 or HTML 4.01) specifies a different content model, with frameset replacing body, that contains either frame elements, or optionally noframes with a body.
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Summary of specification versions
As this list demonstrates, the loose versions of the specification are maintained for legacy support. However, contrary to popular misconceptions, the move to XHTML does not imply a removal of this legacy support. Rather the X in XML stands for extensible and the W3C is modularizing the entire specification and opening it up to independent extensions. The primary achievement in the move from XHTML 1.0 to XHTML 1.1 is the modularization of the entire specification. The strict version of HTML is deployed in XHTML 1.1 through a set of modular extensions to the base XHTML 1.1 specification. Likewise, someone looking for the loose (transitional) or frameset specifications will find similar extended XHTML 1.1 support (much of it is contained in the legacy or frame modules). The modularization also allows for separate features to develop on their own timetable. So for example, XHTML 1.1 will allow quicker migration to emerging XML standards such as MathML (a presentational and semantic math language based on XML) and XForms—a new highly advanced web-form technology to replace the existing HTML forms.
In summary, the HTML 4.01 specification primarily reined in all the various HTML implementations into a single clearly written specification based on SGML. XHTML 1.0, ported this specification, as is, to the new XML defined specification. Next, XHTML 1.1 takes advantage of the extensible nature of XML and modularizes the whole specification. XHTML 2.0 will be the first step in adding new features to the specification in a standards-body-based approach.
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Hypertext features not in HTML
HTML lacks some of the features found in earlier hypertext systems, such as typed links, source tracking, fat links and others.[61] Even some hypertext features that were in early versions of HTML have been ignored by most popular web browsers until recently, such as the link element and in-browser Web page editing.
Sometimes Web services or browser manufacturers remedy these shortcomings. For instance, wikis and content management systems allow surfers to edit the Web pages they visit.
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WYSIWYG editors
There are some WYSIWYG editors (What You See Is What You Get), in which the user lays out everything as it is to appear in the HTML document using a graphical user interface (GUI), where the editor renders this as an HTML document, no longer requiring the author to have extensive knowledge of HTML.
The WYSIWYG editing model has been criticized,[62][63] primarily because of the low quality of the generated code; there are voices advocating a change to the WYSIWYM model (What You See Is What You Mean).
WYSIWYG editors remains a controversial topic because of their perceived flaws such as:
Relying mainly on layout as opposed to meaning, often using markup that does not convey the intended meaning but simply copies the layout.[64]
Often producing extremely verbose and redundant code that fails to make use of the cascading nature of HTML and CSS.
Often producing ungrammatical markup often called tag soup.
As a great deal of the information in HTML documents is not in the layout, the model has been criticized for its 'what you see is all you get'-nature.[65]
Nevertheless, since WYSIWYG editors offer convenience over hand-coded pages as well as not requiring the author to know the finer details of HTML, they still dominate web authoring.[citation needed]
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See also
Breadcrumb (navigation)
CSS
Dynamic web page
HTML decimal character rendering
HTTP
List of document markup languages
Microformat
SGML
XML
