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.
History of HTLM
Origins
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, which was accepted by CERN.
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. It describes 22 elements comprising the initial, relatively simple design of HTML. Thirteen of these elements still exist in HTML 4.
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.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.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.
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 1866, HTML 2.0 included ideas from the HTML and HTML+drafts .There was no "HTML 1.0"; the 2.0 designation was intended to distinguish the new edition from previous drafts.
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.
Version types in HTML
HTML has been developed extensively over the years:
1992
HTML is first defined
1993
HTML+ (some physical layout, fill-out forms, tables, math)
1994
HTML 2.0 (standard for core features)
HTML 3.0 (an extension of HTML+ submitted as a draft standard)
1995
Netscape-specific non-standard HTML appears
1996
Competing Netscape and Explorer versions of HTML
HTML 3.2 (standard based on current practices)
1997
HTML 4.0 (separates structure and presentation with stylesheets)
1999
HTML 4.01 (slight modifications only)
2000
XHTML 1.0 (XML version of HTML 4.01)
2001
XHTML 1.1 (modularization to allow different subsets)
2002
XHTML 2.0 (simplifying and generalizing several tags)
HTML markup
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, which specifies the Document Type Definition.[citation needed] As of HTML 5, no Document Type Definition will need to be specified, and will only determine the layout mode.
Delivery of HTML
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 e-mail
HTTP
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 metadata usually includes the MIME type (e.g. text/html or application/xhtml+xml) and the character encoding (see Character encodings 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, and 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. The current XHTML 1.1 Working Draft also states that XHTML 1.1 documents should be labeled with either MIME type.
