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The link above is for Personas for Firefox. This allows very easy modification of appearance of horizontal bars. Once the add on is installed, you can change themes without closing the browser. May work best on Firefox 3 beta versions, but is compatible with Firefox 2. If you still use Firefox 1, or don't use a Firefox browser and think 3 beta (beta is a test version) is too big a jump, download Firefox 2 from the side bar on this blog.