HTML Version Timeline

November 1995
HTML 2.0 was published as IETF RFC 1866. Supplemental RFCs added capabilities:

November 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)
In June 2000, all of these were declared obsolete/historic by RFC 2854.

January 1997

HTML 3.2 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 1997.

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. A markup for mathematical formulas similar to that in HTML wasn't standardized until 14 months later in MathML.

December 1997
HTML 4.0 was published as a W3C Recommendation. It offers three "flavors":

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", 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.

April 1998
HTML 4.0 was reissued with minor edits without incrementing the version number.

December 1999
HTML 4.01 was published as a W3C Recommendation. It offers the same three flavors as HTML 4.0, and its last errata were published May 12, 2001.

May 2000
ISO/IEC 15445:2000 ("ISO HTML", based on HTML 4.01 Strict) was published as an ISO/IEC international standard.

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.

Drafts

October 1991
HTML Tags, an informal CERN document listing twelve HTML tags, was first mentioned in public. November 1992.

July 1993
Hypertext Markup Language was published by the IETF as an Internet-Draft (a rough proposal for a standard). It expired in January 1994.

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 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.

A demonstration appeared in W3C's own Arena browser. HTML 3.0 did not succeed for several reasons. The pace of browser development, as well as the number of interested parties, had outstripped the resources of the IETF. Netscape continued to introduce HTML elements that specified the visual appearance of documents, contrary to the goals of the newly-formed W3C, which sought to limit HTML to describing logical structure. Microsoft, a newcomer at the time, played to all sides by creating its own tags, implementing Netscape's elements for compatibility, and supporting W3C features such as Cascading Style Sheets.

January 2008
HTML5 was published as a Working Draft by the W3C.

Although its syntax closely resembles that of SGML, HTML 5 has abandoned any attempt to be an SGML application, and has explicitly defined its own "html" serialization, in addition to an alternative XML