Understanding CSS is not trivial stuff. But the Firebug plugin (http://www.getfirebug.com) for Firefox can help. Here's a video I produced that shows how to inspect your CSS with Firebug. The context is understanding Blogger templates:
Also depicted in the video are cross-hairs from the Orca screen magnifier, an application for disabled people that is installed with the Fedora 7 distribution. I used the cross-hairs because the mouse cursor disappears when I capture the video with Cinelerra.