Can you copyright a css file? Can you grab another sites css and use it (provided you change gaphics, etc) without having to worry about copyright issues?
CSS definitions are probably too generic, so it would be a nightmare trying to enforce the copyright. HOWEVER, I wouldn't just take someone else's work and use it, no matter the legalities. If you don't want your stuff to be stolen, don't steal other people's stuff.
Nothing like a little spam to go with your post. As to the CSS, a collection can be put under copyright, so if you just copy the whole thing, you are infringing. But, there's nothing saying you can't learn from and borrow parts. I can't imagine why you'd copy someone's CSS 100% anyway, unless you were copying their entire site.