Firefox 3 is still in beta, but there is already a number of extensions and themes. For all people who have been looking for a way to get Vista’s glass effect in Firefox, look no further. Here is an extension for Firefox 3 that will do it. It will work on the Vista Basic theme, but will not produce the blue toolbars as Windows Explorer does.
Download: Glasser Installer (XPI)
To install Glasser, first download the file, then drag and drop it to your Firefox window.
You can also get the Windows Explorer, Windows Media Player, or Windows Mail style background style on the personal toolbar, for this download GlasserExtras.zip. You can install the CSS files with either the Stylish Add-on, or by edit your userChrome.css file.