HTML 4.0 Specification
The official status of HTML as sanctioned by the World Wide Web Consortium.
Index DOT Html
A comprehensive listing of HTML tags, attributes, and values, as well as their compatibility with the various browsers.
Cascading Style Sheets Specification (CSS1)
The official status of style sheets as sanctioned by the World Wide Web Consortium.
Web Review's Style Sheets Reference Guide
A guide to what styles are and in which browsers they work.
Cascading Style Sheets Positioning Specification (CSS-P)
The official status of positioning (what Dreamweaver calls layers) as sanctioned by the World Wide Web Consortium.