1. Introduction and background
HTML has been in use in the World Wide Web information infrastructure since 1990, and specified in various informal documents. The text/html media type was first officially defined by the IETF HTML working group in 1995 in [HTML20]. Extensions to HTML were proposed in [HTML30], [UPLOAD], [TABLES], [CLIMAPS], and [I18N].
The IETF HTML working group closed Sep 1996, and work on defining HTML moved to the World Wide Web Consortium (W3C). The proposed extensions were incorporated to some extent in [HTML32], and to a larger extent in [HTML40]. The definition of multipart/form-data from [UPLOAD] was described in [FORMDATA]. In addition, a reformulation of HTML 4.0 in XML 1.0[XHTML1] was developed.
[HTML32] notes "This specification defines HTML version 3.2. HTML 3.2 aims to capture recommended practice as of early '96 and as such to be used as a replacement for HTML 2.0 (RFC 1866hist(-> 2854))." Subsequent specifications for HTML describe the differences in each version.
In addition to the development of standards, a wide variety of additional extensions, restrictions, and modifications to HTML were popularized by NCSA's Mosaic system and subsequently by the competitive implementations of Netscape Navigator and Microsoft Internet Explorer; these extensions are documented in numerous books and online guides.