While not directly related to PHP, there's a new article over on DevArticles.com pertaining to CSS and how to get started.

In CSS: Where Little Things Mean a Lot the author explains a bit about what CSS is and how you can benefit from using it. He then moves into a simple example (a very simple example) to expose coders out there to the format of the files and how to link to them internally from your HTML. The next logical step, of course, is something a bit more difficult - using CSS with a DIV tag. The illustration gives you an idea of how to connect the classes from the CSS document to the items (such as the DIV) in your file.

This article is a good, very basic place to start, but just about anyone will want to branch out from there. To get into some of the real "meat" of CSS, check out the w3schools.com section for all of the details...