I would certainly follow "just a pod's" advice above.
Also go to a good bookshop and browse through all they have and find something that covers what you need.
A book I have found that gives a good introduction is:-
SAMS teach yourself CSS in 24 hours by Kynn Bartlett
I'll add a vote for any of Eric Meyer's books. I read a couple when I first started and that's pretty much all it took to teach me CSS. I highly recommend them.
__________________ l Search Engine Friendly Web Design | Please login or register to view this content. Registration is FREE
l Tips On Marketing, SEO, Design, and Development | Please login or register to view this content. Registration is FREE
If starting from complete scratch (as I was -- totally great at tables, did not know was CSS was!): Head First HTML with CSS and XHTML by Elisabeth Freeman and Eric Freeman really got me going -- suddenly I knew what CSS was and even a good bit how to start. Then went on to Eric Meyers and others.