http://www.reitix.com/Makaleler/HTML-Versiyonlari/ID=920
http://www.yourhtmlsource.com/starthere/historyofhtml.html

HTML Version Usage Over Time
The following graph shows how the number of resources that used a given version of the HTML format, as a fraction of all HTML resources, by year.

Each new version comes to dominate the picture, then slowly fade away. Over time, more versions are present in each crawl, with HTML 2.0-4.01 and XHTML 1.0-1.1 all present in the 2010 crawl data.