Recently the folks at SitePoint.com launched two excelent online reference sites for web designers and developers, the first one is the SitePoint CSS Reference and the second one is the SitePoint HTML Reference (Beta).

Both of them are free and available to anyone and everyone who needs to lookup any information related to CSS and HTML in an easy and fast way. The SitePoint HTML Reference (Beta) is still in progress. Also, both of them are very detailed and up-to-date on each subject and are focused not only to beginners because they covers from general to advanced topics.

The SitePoint CSS Reference website covers topics like:

• What Is CSS?
• General Syntax and Nomenclature
• At-rules and Selector Reference
• The Cascade, Specificity, and Inheritance
• Color, Backgrounds, CSS Layout and Formatting.
• Box, Layout, List, Typographical and Table Properties.
• Workarounds, Filters, and Hacks
• Differences Between HTML and XHTML

The SitePoint HTML Reference (Beta) website covers topics like:

• HTML Concepts
• Structural, Head, List, Text Formatting, Form, Image and Media Elements
• Table, Frame and Window Elements
• Microformats and Common Attributes
• Elements and Valid DTDs They May Appear In
• Deprecated Elements (to avoid using)
• Proprietary/Non-standard Elements (to avoid using)

So, if you need information related with these subjects don't waiste your time and visit them.

Best regards,

Also, the CSS reference from W3Schools can be found at:
http://www.w3schools.com/css/css_reference.asp
It contains more advanced information about CSS including browser support for certain CSS syntax.

Excellent CSS reference especially the examples pages.

Best regards,