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Forum Moderators: not2easy
There is a lot of talent in this forum, and quite a number far better than I, keep reading, check out the library and you'll soon work out who the players are!
I've always found the best learning is acheived by doing but you need a good reference. w3schools have a nice course, so does westciv.com - the best is w3c however, just think about what you want to do then look down the specs list [webmasterworld.com] and follow the appropriate link.
CSS isn't really about 'knowing every technical detail' for me. You have to have a feel for the technology, and know where to get specific info on a property or concept.
By continully reading and asking questions here and using the references above you'll soon have a feel for it, and once ou have that, css is really very simple ;)
Easy to read, easy to understand, and has plenty of examples. I suppose the content may be a bit old nowadays, but I'd still recommend it as a solid foundation for CSS study.