All about HTML - HyperText Markup Language:

HTML 2.0 accessible as:
1. HTML document, 2. PostScript document, 3. Plain text file.
HTML 3.0 accessible as:
1. HTML document.
HTML 3.2 accessible as:
1. HTML document.
HTML 4.0 accessible as:
1. HTML document.
Netscape extensions to the HTML 2.0:
1. from netscape.com, 2. from www.mcom.com.
Netscape extensions to the HTML 3.0:
1. from netscape.com.
From HTML2.0 to HTML3.0 and Extensions to HTML.
Baby's guide to the HTML.
HTML quick reference.
HTML, the complete-ish guide by Sunil Gupta.
HTML Reference by Michael Hannah (mjhanna@sandia.gov).
An index of HTML codes.
Basic HTTP.
Mozilla DTD.
Frame syntax.

And here you can see more information.