The latest and greatest is actually XHTML 1.0, which is a reformulation of HTML 4.01 in XML.
But if you're coding in HTML, you should go by the HTML 4.01 recommendations. It's a lot like software versions, version 4.0 is an improved upon version of 3.2 which fixed certain rendering errors and improved upon accessibility, and better support for stylesheets and scripting languages etc...
Read all about it
here