Some recommended URL's for learning about HTML
A set of definitive documents about html 4 from --
about (from their self-description):  A discussion and introduction of html 4 from W3C. 

HTML Basics -- from MDN (Mozilla) -- I think the Mozillians keep this up to date. It is authoratative and covers HTML5 as well as HTML4.

Getting started with HTML -- 2005, by Jukka Korpela of Finland (I think Jukka may have been a student of mine once?)

HTML Primer 1996 from NCSA (the National Center for Supercomputer Applications) is where Mosaic (the precursor to Netscape) was developed. The Primer is elementary, but nice.

Some notes on html by DDailey