Firefox 4 Tips and Tricks
Get the old style Menu Bar in Firefox
As you know, the new Firefox has completely revamped the menu bar. If you want it back the way it used to be in Firefox 3, do the following:
Click the Firefox down arrow to expand it and then under customize sub menu check Menu bar as shown in the image below.
Once you click this option, you will see the old classic style menu bar back in new firefox 4.