OrientaleCuisine.com

QuirksMode - CSS contents and browser compatibility
Tests of CSS2 selectors, pseudoclasses and declarations, including compatibility information for Explorer, Mozilla, Safari, and Opera.
www.quirksmode.org/

WestCiv - CSS1 and CSS2 Browser Support
Groups properties by level of support. Contains guide, tutorials, and articles.
www.westciv.com/

Cascading Style Sheets Level 1 Browser Incompatibilities
Teaches how to produce Web pages (formatted with Cascading Style Sheets Level 1) that display attractively on modern browsers and adequately on recent ones.
www.ctlow.ca/

Validator CSS
W3C CSS validation service.
jigsaw.w3.org/

WebReview.com's Style Sheet Reference Guide
Offers browser compatibility charts, links to articles, and an FAQ. Registration required.
www.ddj.com/

CSS Test Matrix
Features tests on various properties according to the CSS1 specification.
www.mozilla.org/

Official CSS1 Test Suite from the W3C
Provided as a way for vendors and page authors to test their browser's conformance to the CSS1 specification.
www.w3.org/

RichInStyle.com CSS2 Tests
Covers all of CSS2.
www.richinstyle.com/

Rendertests
CSS pages that can used to test with different browsers.
realdev1.realise.com/

Centricle - CSS Filters
Table indicating which browsers are affected by the various methods used to hide CSS. Includes test cases for each technique, as well as user contributed comments.
centricle.com/