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| HTML (HyperText Markup Language) | |
|---|---|
| |
| File extension: | .html, .htm
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| MIME type: | text/html
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| Type code: | TEXT |
| Uniform Type Identifier: | public.html |
| Developed by: | World Wide Web Consortium |
| Type of format: | Markup language |
| Extended from: | SGML |
| Extended to: | XHTML |
HTML, an initialism of HyperText Markup Language, is the predominant markup language for web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as links, headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of tags, surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) which can affect the behavior of web browsers and other HTML processors.
HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML-descended form (such as XHTML 1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).
By convention, html format data files use a file extension .html or .htm.
Contents |
In 1980, physicist Tim Berners-Lee, who was an independent contractor at CERN, proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents. In 1989, Berners-Lee and CERN data systems engineer Robert Cailliau each submitted separate proposals for an Internet-based hypertext system providing similar functionality. The following year, they collaborated on a joint proposal, the WorldWideWeb (W3) project,Tim Berners-Lee, "Information Management: A Proposal." CERN (March 1989, May 1990). http://www.w3.org/History/1989/proposal.html which was accepted by CERN.
The first publicly available description of HTML was a document called HTML Tags, first mentioned on the Internet by Berners-Lee in late 1991.HTML Tags. World Wide Web Consortium. Retrieved on 2007-04-08.First mention of HTML Tags on the www-talk mailing list. World Wide Web Consortium (1991-10-29). Retrieved on 2007-04-08. It describes 22 elements comprising the initial, relatively simple design of HTML. Thirteen of these elements still exist in HTML 4.Index of elements in HTML 4. World Wide Web Consortium (1999-12-24). Retrieved on 2007-04-08.
Berners-Lee considered HTML to be, at the time, an application of SGML, but it was not formally defined as such until the mid-1993 publication, by the IETF, of the first proposal for an HTML specification: Berners-Lee and Dan Connolly\'s "Hypertext Markup Language (HTML)" Internet-Draft, which included an SGML Document Type Definition to define the grammar.Tim Berners-Lee (1991-12-09). Re: SGML/HTML docs, X Browser (archived www-talk mailing list post). Retrieved on 2007-06-16. “SGML is very general. HTML is a specific application of the SGML basic syntax applied to hypertext documents with simple structure.” The draft expired after six months, but was notable for its acknowledgment of the NCSA Mosaic browser\'s custom tag for embedding in-line images, reflecting the IETF\'s philosophy of basing standards on successful prototypes.Raymond, Eric. "IETF and the RFC Standards Process", The Art of Unix Programming. “In IETF tradition, standards have to arise from experience with a working prototype implementation — but once they become standards, code that does not conform to them is considered broken and mercilessly scrapped. …Internet-Drafts are not specifications, and software implementers and vendors are specifically barred from claiming compliance with them as if they were specifications. Internet-Drafts are focal points for discussion, usually in a working group… Once an Internet-Draft has been published with an RFC number, it is a specification to which implementers may claim conformance. It is expected that the authors of the RFC and the community at large will begin correcting the specification with field experience.” 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.HTML+ Internet-Draft - Abstract. “Browser writers are experimenting with extensions to HTML and it is now appropriate to draw these ideas together into a revised document format. The new format is designed to allow a gradual roll over from HTML, adding features like tables, captioned figures and fill-out forms for querying remote databases or mailing questionnaires.”
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. Published as Request for Comments 1996, HTML 2.0 included ideas from the HTML and HTML+ drafts.RFC 1866: Hypertext Markup Language - 2.0 - Acknowledgments. Internet Engineering Task Force (2005-09-22). Retrieved on 2007-06-16. “Since 1993, a wide variety of Internet participants have contributed to the evolution of HTML, which has included the addition of in-line images introduced by the NCSA Mosaic software for WWW. Dave Raggett played an important role in deriving the forms material from the HTML+ specification. Dan Connolly and Karen Olson Muldrow rewrote the HTML Specification in 1994. The document was then edited by the HTML working group as a whole, with updates being made by Eric Schieler, Mike Knezovich, and Eric W. Sink at Spyglass, Inc. Finally, Roy Fielding restructured the entire draft into its current form.” There was no "HTML 1.0"; the 2.0 designation was intended to distinguish the new edition from previous drafts.RFC 1866: Hypertext Markup Language - 2.0 - Introduction. Internet Engineering Task Force (2005-09-22). Retrieved on 2007-06-16. “This document thus defines an HTML 2.0 (to distinguish it from the previous informal specifications). Future (generally upwardly compatible) versions of HTML with new features will be released with higher version numbers.”
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). 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.
| HTML |
|---|
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Character encodings |
July, 1993: Hypertext Markup Language, was published at IETF working draft (that is: not a standard – yet).
November, 1995: HTML 2.0 published as IETF Request for Comments:
Ultimately, all were declared obsolete/historic by RFC 2854 in June 2000.
An HTML 3.0 standard was proposed to the IETF by Dave Raggett and the newly formed W3C in April 1995. It proposed 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 math elements.HyperText Markup Language Specification Version 3.0. Retrieved on 2007-06-16. Even though it was designed to be compatible with HTML 2.0, it was too complex at the time to be implemented. Browser vendors opted to support only parts of the proposal, but implemented other markup constructs that they wanted to be incorporated into the standard.Extensions to HTML 3.0. Netscape. “Netscape remains committed to supporting HTML 3.0. To that end, we\'ve gone ahead and implemented several of the more stable proposals, in expectation that they will be approved. …In addition, we\'ve also added several new areas of HTML functionality to Netscape Navigator that are not currently in the HTML 3.0 specification. We think they belong there, and as part of the standards process, we are proposing them for inclusion.” When the draft expired in September 1995, work in this direction was discontinued due to lack of browser support. HTML 3.1 was never officially proposed, and the next standard proposal was HTML 3.2 (code-named "Wilbur"), which dropped the majority of the new features in HTML 3.0 and instead adopted many browser-specific element types and attributes that had been created for the Netscape and Mosaic web browsers.Arnoud Engelfriet. Introduction to Wilbur. Web Design Group. Retrieved on 2007-06-16.
January 14, 1997: HTML 3.2, published as a W3C Recommendation.
HTML 3.2 was never submitted to the IETF, whose HTML Working Group closed in September 1996;IETF HTML WG. Retrieved on 2007-06-16. “NOTE: This working group is closed” it was instead published as one of the W3C\'s first "Recommendations" in early 1997. Math support as proposed by HTML 3.0 finally came about years later with a different standard, MathML.
December 18, 1997: HTML 4.0, published as a W3C Recommendation. It offers three "flavors":
HTML 4.0 (initially code-named "Cougar") likewise adopted many browser-specific element types and attributes, but at the same time began to try to "clean up" the standard by marking some of them as deprecated, and suggesting they not be used. Minor editorial revisions to the HTML 4.0 specification were published in 1998 without incrementing the version number and further minor revisions as HTML 4.01.
April 24, 1998: HTML 4.0 was reissued with minor edits without incrementing the version number.
December 24, 1999: HTML 4.01, published as a W3C Recommendation. It offers the same three flavors as HTML 4.0, and its last errata was published May 12, 2001.
HTML 4.01 and ISO/IEC 15445:2000 are the most recent and final versions of HTML.
May 15, 2000: ISO/IEC 15445:2000 ("ISO HTML", based on HTML 4.01 Strict), published as an ISO/IEC international standard.
January 22, 2008: HTML 5, published as a Working Draft by W3C.
XHTML is a separate language that began as a reformulation of HTML 4.01 using XML 1.0. It continues to be developed:
HTML markup consists of several key components, including elements (and their attributes), character-based data types, and character references and entity references. Another important component is the document type declaration.
Elements are the basic structure for HTML markup. Elements have two basic properties: attributes and content. Each attribute and each element\'s content has certain restrictions that must be followed for an HTML document to be considered valid. An element usually has a start tag (e.g. ). The element\'s attributes are contained in the start tag and content is located between the tags (e.g.
Structural markup describes the purpose of text. For example, Golf
Presentational markup describes the appearance of the text, regardless of its function. For example boldface indicates that visual output devices should render "boldface" in bold text, but gives no indication what devices which are unable to do this (such as aural devices that read the text aloud) should do. In the case of both bold and italic, there are elements which usually have an equivalent visual rendering but are more semantic in nature, namely strong emphasis and emphasis 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 CSS based style design.
Hypertext markup links parts of the document to other documents. HTML up through version XHTML 1.1 requires the use of an anchor element to create a hyperlink in the flow of text: Wikipedia. However, the href attribute must also be set to a valid URL so for example the HTML code,
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).www.w3.org/TR/html401/intro/sgmltut.html#h-3.2.2.www.w3.org/TR/xhtml1/diffs.html#h-4.4. Leaving attribute values unquoted is considered unsafe.www.cs.tut.fi/~jkorpela/qattr.html. In contrast with name-value pair attributes, there are some attributes that have effect on the element simply by their presence in the start tag of the elementwww.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/Tags.html. (like ismap attribute for img elementwww.w3.org/TR/1999/REC-html401-19991224/struct/objects.html#adef-ismap.).
Most elements take any of several common attributes: id, class, style and title. Most also take language-related attributes: lang and dir.
The id attribute provides a document-wide unique identifier for an element. This can be used by stylesheets to provide presentational properties, by browsers to focus attention on the specific element or by scripts to alter the contents or presentation of an element. The class attribute provides a way of classifying similar elements for presentation purposes. For example, an HTML document (or a set of documents) may use the designation class="notation" to indicate that all elements with this class value are all subordinate to the main text of the document (or documents). Such notation classes of elements might be gathered together and presented as footnotes on a page, rather than appearing in the place where they appear in the source HTML.
An author may use the style non-attributal codes presentational properties to a particular element. It is considered better practice to use an element’s son- id page and select the element with a stylesheet, though sometimes this can be too cumbersome for a simple ad hoc application of styled properties. The title is used to attach subtextual explanation to an element. In most browsers this title attribute is displayed as what is often referred to as a tooltip. The generic inline span element can be used to demonstrate these various non-attributes.
The preceding displays as HTML (pointing the cursor at the abbreviation should display the title text in most browsers).
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 equivalent 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 elements or the values of attributes. The double-quote character, ", when used to quote an attribute value, must also be escaped as """ or """ or """ when it appears within in the attribute value itself. The single-quote character, \', when used to quote an attribute value, must also be escaped as "'" or "'" (should NOT be escaped as "'" unless in XHTML documents) when it appears within in the attribute value itself. However, since document authors often overlook the need to escape these characters, browsers tend to be very forgiving, treating them as markup only when subsequent text appears to confirm that intent.
Escaping also allows for characters that are not easily typed or that aren\'t even available in the document\'s character encoding to be represented within the element and attribute content. For example, "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. The characters comprising those references (that is, the "&", the ";", the letters in "eacute", and so on) are available on all keyboards and are supported in all character encodings, whereas the literal "é" is not.
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.
In order to enable Document Type Definition (DTD)-based validation with SGML tools and in order to avoid the quirks mode in browsers, HTML documents can start with a Document Type Declaration (informally, a "DOCTYPE"). The DTD to which the DOCTYPE refers contains machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers do not necessarily read the DTD, however. The most popular graphical browsers use DOCTYPE declarations (or the lack thereof) and other data at the beginning of sources to determine which rendering mode to use.
For example:
This declaration references the Strict DTD of HTML 4.01, which does not have presentational elements like , leaving formatting to Cascading Style Sheets and the span and div tags. SGML-based validators read the DTD in order to properly parse the document and to perform validation. In modern browsers, the HTML 4.01 Strict doctype activates standards layout mode for CSS as opposed to quirks mode.
In addition, HTML 4.01 provides Transitional and Frameset DTDs. The Transitional DTD was intended to gradually phase in the changes made in the Strict DTD, while the Frameset DTD was intended for those documents which contained frames.
There is no official specification called "Semantic HTML", though the strict flavors of HTML discussed below are a push in that direction. Rather, semantic HTML refers to an objective and a practice to create documents with HTML that contain only the author\'s intended meaning, without any reference to how this meaning is presented or conveyed. A classic example is the distinction between the emphasis element () and the italics element (). Often the emphasis element is displayed in italics, so the presentation is typically the same. However, emphasizing something is different from listing the title of a book, for example, which may also be displayed in italics. In purely semantic HTML, a book title would use a separate element than emphasized text uses (for example a ), because they are each meaningfully different things.
The goal of semantic HTML requires two things of authors:
The Grapes of Wrath. Here, the Semantic HTML also requires complementary specifications and software compliance with these specifications. Primarily, the development and proliferation of CSS has led to increasing support for semantic HTML because CSS provides designers with a rich language to alter the presentation of semantic-only documents. With the development of CSS the need to include presentational properties in a document has virtually disappeared. With the advent and refinement of CSS and the increasing support for it in web browsers, subsequent editions of HTML increasingly stress only using markup that suggests the semantic structure and phrasing of the document, like headings, paragraphs, quotes, and lists, instead of using markup which is written for visual purposes only, like , (bold), and (italics). Some of these elements are not permitted in certain varieties of HTML, like HTML 4.01 Strict. CSS provides a way to separate document semantics from the content\'s presentation, by keeping everything relevant to presentation defined in a CSS file. See separation of style and content.
Semantic HTML offers many advantages. First, it ensures consistency in style across elements that have the same meaning. Every heading, every quotation, every similar element receives the same presentation properties.
Second, semantic HTML frees authors from the need to concern themselves with presentation details. When writing the number two, for example, should it be written out in words ("two"), or should it be written as a numeral (2)? A semantic markup might enter something like
A third advantage is device independence and repurposing of documents. A semantic HTML document can be paired with any number of stylesheets to provide output to computer screens (through web browsers), high-resolution printers, handheld devices, aural browsers or braille devices for those with visual impairments, and so on. To accomplish this nothing needs to be changed in a well coded semantic HTML document. Readily available stylesheets make this a simple matter of pairing a semantic HTML document with the appropriate stylesheets (of course, the stylesheet\'s selectors need to match the appropriate properties in the HTML document).
Some aspects of authoring documents make separating semantics from style (in other words, meaning from presentation) difficult. Some elements are hybrids, using presentation in their very meaning. For example, a table displays content in a tabular form. Often this content only conveys the meaning when presented in this way. Repurposing a table for an aural device typically involves somehow presenting the table as an inherently visual element in an audible form. On the other hand, we frequently present lyrical songs — something inherently meant for audible presentation — and instead present them in textual form on a web page. For these types of elements, the meaning is not so easily separated from their presentation. However, for a great many of the elements used and meanings conveyed in HTML, the translation is relatively smooth.
HTML documents can be delivered by the same means as any other computer file; however, HTML documents are most often delivered in one of the following two forms: Over HTTP servers and through email.
The World Wide Web is primarily composed of HTML documents transmitted from a web server to a web browser using the Hypertext Transfer Protocol (HTTP). However, HTTP can be used to serve images, sound and other content in addition to HTML. To allow the web browser to know how to handle the document it received, an indication of the file format of the document must be transmitted along with the document. This vital metadata includes the MIME type (text/html for HTML 4.01 and earlier, application/xhtml+xml for XHTML 1.0 and later) and the character encoding (see Character encodings in HTML).
In modern browsers, the MIME type that is sent with the HTML document affects how the document is interpreted. A document sent with an XHTML MIME type, or served as application/xhtml+xml, is expected to be well-formed XML and a syntax error causes the browser to fail to render the document. The same document sent with an HTML MIME type, or served as text/html, might get displayed since web browsers are more lenient with HTML. However, XHTML parsed this way is not considered either proper XHTML or HTML, but so-called tag soup.
If the MIME type is not recognized as HTML, the web browser should not attempt to render the document as HTML, even if the document is prefaced with a correct Document Type Declaration. Nevertheless, some web browsers do examine the contents or URL of the document and attempt to infer the file type, despite this being forbidden by the HTTP 1.1 specification.
Most graphical e-mail clients allow the use of a subset of HTML (often ill-defined) to provide formatting and semantic markup capabilities not available with plain text, like emphasized text, block quotations for replies, and diagrams or mathematical formulas that could not easily be described otherwise. Many of these clients include both a GUI editor for composing HTML e-mails and a rendering engine for displaying received HTML e-mails. Use of HTML in e-mail is controversial due to compatibility issues, because it can be used in phishing/privacy attacks, because it can confuse spam filters, and because the message size is larger than plain text.
The most common filename extension for files containing HTML is .html. A common abbreviation of this is .htm; it originates from older operating systems and file systems, such as the DOS versions from the 80s and early 90s and FAT, which limit file extensions to three letters. Both forms are widely supported by browsers.
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, 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 and to create a rational foundation to build 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 within the specification.
There are two axes differentiating various flavors of HTML as currently specified: SGML-based HTML versus XML-based HTML (referred to as XHTML) on the one axis and strict versus transitional (loose) versus frameset on the other axis.
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 clearly distinguish it 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, sometimes they are documented in parallel. In such circumstances some authors conflate the two names as (X)HTML or X(HTML).See e.g., XHTML#Relationship to HTML
Like HTML 4.01, XHTML 1.0 has three sub-specifications: strict, loose 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 — is 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 or 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:
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:
lang attribute rather than the XHTML xml:lang attribute XHTML uses XML\'s built in language defining functionality attribute.
xmlns=URI). HTML has no facilities for namespaces.
Content-Type header sent by the server.
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:
xml:lang and lang attributes on any elements assigning language.
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 which are XHTML 1.0 and have been made compatible in this way, the W3C permits them to the 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.
The latest SGML-based specification HTML 4.01 and the earliest XHTML version include three sub-specifications: Strict, Transitional (once called Loose), and Frameset. The Strict variant represents the standard proper, whereas the Transitional and Frameset variants were developed to assist in the transition from earlier versions of HTML (including HTML 3.2). The Transitional and Frameset variants allow for presentational markup whereas the Strict variant encourages the use of style sheets through its omission of most presentational markup.
The primary differences which make the Transitional variant more permissive than the Strict variant (the differences as the same in HTML 4 and XHTML 1.0) are:
body, blockquote, form, noscript and noframes
u)
s and strike)
center
font
basefont
background and bgcolor attributes for body element.
align attribute on div, form, paragraph (p), and heading (h1...h6) elements
align, noshade, size, and width attributes on hr element
align, border, vspace, and hspace attributes on img and object elements
align attribute on legend and caption elements
align and bgcolor on table element
nowrap, bgcolor, width, height on td and th elements
bgcolor attribute on tr element
clear attribute on br element
compact attribute on dl, dir and menu elements
type, compact, and start attributes on ol and ul elements
type and value attributes on li element
width attribute on pre element
menu list (no substitute, though unordered list is recommended; may return in XHTML 2.0 specification)
dir list (no substitute, though unordered list is recommended)
isindex (element requires server-side support and is typically added to documents server-side)
applet (deprecated in favor of object element)
pre element does not allow: applet, font, and basefont (elements not defined in strict DTD)
language attribute on script element (presumably redundant with type attribute, though this is maintained for legacy reasons).
frameset element (used in place of body for frameset DTD)
frame element
iframe
noframes
target attribute on anchor, client-side image-map (imagemap), link, form, and base elements
In addition to the above transitional differences, the frameset specifications (whether XHTML 1.0 or HTML 4.01) specifies a different content model:
Any of the various head related elements.
As this list demonstrates, the loose flavors 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 clear 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.
HTML lacks some of the features found in earlier hypertext systems, such as typed links, transclusion, source tracking, fat links, and more.Jakob Nielsen (2005-01-03). Reviving Advanced Hypertext. Retrieved on 2007-06-16. 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.
Wikibooks has more on the topic of
| Standards of the World Wide Web Consortium | |
|---|---|
| Recommendations | CDF · CGI · CSS · DOM · HTML · MathML · OWL · RDF · RDF Schema · SISR · SMIL · SOAP · SRGS · SSML · SVG · Timed Text · VoiceXML · WSDL · XACML · XForms · XHTML · XML · XML Base · XML Events · XML Information Set · XML Schema (W3C) · XML Signature · XPath · XPointer · XQuery · XSL Transformations · XSL-FO · XSL · XLink |
| Notes | XHTML+SMIL · XAdES |
| Working drafts | CCXML · CURIE · InkML · XFrames · XFDL · WICD · XHTML+MathML+SVG |
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