I agree, the Zen Garden site is really neat. This version of the Zen Garden has an “elastic” layout which allows you to increase the font size while maintaining the formatting. It’s amazing what CSS can do. Of course not all sites need to be as fancy as the Zen Garden site, but it’s a good example to show the power of CSS.
Here is a good tutorial: http://www.w3schools.com/css/default.asp
I also have the following links bookmarked. You might find these links useful at a later date, once you get up to speed on the basics of CSS.
http://catcode.com/csstips/classes.html
http://moronicbajebus.com/playground/cssplay/hormenu/
http://checkweight.com/layout.html
http://www.alistapart.com/articles/taminglists/
http://www.fu2k.org/alex/css/layouts/3Col_NN4_FMFM.mhtml
http://www.stopdesign.com/articles/absolute/
http://www.netmechanic.com/news/vol5/css_no12.htm