As per my choice, Firefox is the No 1 Browser in the world and millions of users are using it since more than 3years. In firefox out of the box has a very grey and boring theme, that doesn’t sit well with Windows 7, but this can be improved by installing this Firefox theme for Windows 7. The Windows 7 theme currently only works with Firefox 3.5, but full 3.6 support will probably be added once its beta is over.
%appdata%/Mozilla/Firefox/Profiles// and reopen Firefox. To get the Aero Glass effect you also need to install the Firefox Addon Glasser.
