Create the file “userChrome.css”; there may already be an example file that you can just rename. The important bit of this CSS file is the namespace line that tells Firefox how to use it.

In case you're not keen on what Stylish does, it allows you to add your own CSS style elements to any web page in much the same way that Greasemonkey lets users add their own Javascript to a web ...

Learn HTML and CSS online for free, and use them to create webpages or move up in your career.