A few weeks ago, I hopefully provided you with the reasoning behind why library web sites have to move from plain HTML to using CSS for style and formatting.
I started to create a tutorial, and got frustrated with WordPress, trying to display code. So, I started looking around the Web, trying to see if I was just recreating the wheel. I found an awful lot, but perhaps the clearest jumping off point for beginners that I found was a series of video on (where else?) YouTube. Check this one out and then watch the whole series to get a step up on learning CSS from the ground up.