If you are using personas or a busy theme, they make things very hard to read. Vista may have transparency but use never kicked in until Windows 7, but a few people did turn it on in Vista. Show an image of what you are talking about, preferably that shows a bit of desktop around it so wee can see if color came from desktop or you can tell us. I don't like much about toolbars after Firefox 2, they get progressively worse so you learn how to customize toolbars and use styles then you've got something much better. The worse things get, the more people learn how to fix things which means far more time is almost certainly spent by hundreds of thousands in fixing things that could have been fixed with less effort up front. See http://dmcritchie.mvps.org/firefox/firefox-problems.htm#fx4styles and the before/after pictures for how styling can change things. You can make Firefox 4.0.1 look like Firefox 3.6.17, see numbered items 1-10 in the following topic [http://dmcritchie.mvps.org/firefox/firefox-problems.htm#fx4interface Fix Firefox 4.0 toolbar user interface, problems (Make Firefox 4.0 look like 3.6)]