From PunBB Resource Wiki
This article comes from the following thread started by Paul: http://forums.punbb.org/viewtopic.php?id=5791
Several excellent guides plus browser compatability chart.
Some cool tutorials
A great tutorial on CSS selectors and how to use them
Everything you wanted to know about floats and were afraid to ask (Well everything apart from why they are such pain to use)
More about containing/clearing floats
Getting fancy with lists and menus
CSS Forum and losts of resources
Bugs, hacks and why your site goes splat in Internet Explorer
IE5 Mac and why it may ruin your day/month/year/life
The css box model in 3D. One look at this graphic and a lot of things become clear.
For inspiration and more links
Articles and tutorials related to accessability issues and an ongoing experiment to make a phpbb forum accessible
Some guru sites and blogs with aricles/tutorials
Lots and lots of links to useful stuff
Zen Garden browser
Open Source designs
Web Developer extension for Firefox 1.0
Sitepoint.com client side tutorials on CSS
Markup and CSS documentation, specifications, 'The Manual'
CSS layouts, tips, tricks, and techniques
Web developer help forum
Cool style generator
Good css editor with autocomplete and edit colors etc.
For XHTML and CSS tutorials
Tools for optimizing style sheets
The Web Developers Handbook. An absolutely massive resource listing for xhtml/css etc some in German as well as English
More about webdesign, but has references to CSS