Books

• Cascading Style Sheets : Designing for the Web (3rd Edition) by Hakon Wium Lie and Bert Bos
• Cascading Style Sheets: The Definitive Guide, 3rd Edition by Eric Meyer
• Eric Meyer on CSS and More Eric Meyer on CSS
• Bulletproof Web Design, 2nd edition, by Dan Cederholm
• Web Standards Solutions: The Markup and Style Handbook by Dan Cederholm
• CSS Cookbook by Christopher Schmitt

Specifications / Resources

• W3C Cascading Style Sheets
• Cascading Style Sheets, Level 1
• Cascading Style Sheets 2.1
• W3C CSS Validation Service