What does HTML 4.0 mean?
Hypertext Markup Language revision 4.0 (HTML 4.0) is a markup language that represents the structure and presentation of web pages. HTML 4.0 was published on December 1997 as a W3C Recommendation.
In addition to previous revisions of HTML, HTML 4.0 supports style sheets, scripting languages, object support, more multimedia options, and improved accessibility for users with disabilities, among other features.
Techopedia explains HTML 4.0
HTML 4.0 extended the previous HTML 3.2 revision into powerful capabilities including ideas never implemented from HTML 3.0 draft. On December 1999, HTML 4.0 was replaced by HTML 4.01 as a minor update correcting minor problems. Thus, HTML 4.01 is the final standard version recommended by W3C.
HTML4 (or HTML 4.01) is constantly evolving. The next revision is HTML 5.0 which has been debated for years and has a very complex process for implementation, though many browsers currently support some of the newer HTML5 features. While HTML 4 will be phased out eventually, it while be a while before everything moves to HTML5.