MAKE FIREFOX 3.5 LOOK LIKE FIREFOX 3.7

Windows only: Mozilla released their version 3.7 theme mockups only a few days ago, but you don't have to wait for the 3.7 release to enjoy them—a motivated user already created a lookalike theme that you can install now.

Installing this theme isn't quite as simple as you are probably used to—you'll need to first enable the All-Glass Firefox extension for the Aero effects, the Personal Menu extension to hide the menubar and add the Tools button, the Stylish extension for a tweak that fixes the text, and then drag the mockup theme's *.jar file into the add-ons window to install it.

Once you've successfully completed all of the steps—which are detailed on the download page—you should have an impressive browser style that looks very similar to the screenshot.


Sources:
http://boneyardbrew.deviantart.com/art/Firefox-3-7-Mockup-Redux-2-5-130502568

http://lifehacker.com/5322073/firefox-37-theme-makes-your-browser-look-awesome