The best way to learn something is by doing. Here is what I find useful for learning CSS:
- Get Firefox if you don’t already have it.
- Install the free Web Developer Extension.
- Go surf to any site you like and click on "Edit CSS" in the CSS menu of the web developer expension.
- This will open up a sidebar that displays the CSS used in the page you are looking at.
- Now the neat thing is that you can edit the CSS code in the sidebar and see the changes in real-time on the page, so called "live editing". Very, very cool. And very, very useful in my opinion to get an handle on CSS, which can sometimes look quite intimidating.
- The extension has lots of other useful features to give you all kinds of information about the site you are viewing.