Custom CSS tutorials/guidelines?

I say, can anyone (on Dth or LJ) tell me how to view a journal style sheet - the bit that actually has pre-written code on it, not just the "write your own bits of code here" slot? I have to learn CSS for work, and while the training videos are informational, I won't really understand it without a playspace to poke around in and a properly written style to take apart.

Pointing me to FAQs about "how to do this specific thing in CSS" would also be helpful. Thanks, anybody!