By setting up CSS styles that your browser applies to every page you visit, you can customize your whole web experience in all kinds of neat ways.
Here are some ideas:
http://www.squarefree.com/userstyles/
And some more great stuff:
http://www.oreillynet.com/pub/a/network/2000/06/30/magazine/mozilla_stylesheets.html
The "important" keyword is useful so that you can make sure your styles override those set by the page author. That's especially important when using a user defined stylesheet to tweak the page display for low-sight or other disabled users.
http://www.w3.org/TR/CSS-access#UserControl
Dated: 04/15/2003