There are stacks of CSS tutorials on the web, I’ve bookmarked many but found most of them disappointing and frankly, lost interest 😉
I mention this because we finally got Seagull mostly Xhtml-ified, with decent CSS, and folks are now complaining they want good old fashioned tables back.
It’s not difficult to sympathise, when you’re used to doing things a certain way for a length of time, jumping from easy table layouts to CSS hacks/trickery can be a pain.
One tutorial I found that presented the basic concepts in an accessible way was Simon Willison’s CSS ain’t Rocket Science. There’s several blog entries here which, along with the comments, give a very well-rounded picture.