"What good is a browser unless you can tweak it, hack it and
bend it to your will? No good at all. The more you can hack it, the
better it is.
"And that means that Firefox must be a great browser. It's
infinitely customizable, via editing a text file called
userChrome.css, making changes via a command called about:config,
and using free add-ons to extend the features of the
browser..."