Professor Tom Wilson writes...
I'm very impressed by the Mozilla Firebird browzer. It may even displace Opera as my preferred system.

One of the big features is the extent to which it can be customised through 'Tips and Tricks' which allow you to do practically anything by inserting code into one or another of three text files: user.js, userChrome.css, and userContent.css

Try it out, I think you'll like it.