Firefox comes with a neat interface. But as you came here, I suppose you expect from your browser more than an average user.
Implicitly, you get long, unnecessary menus and redundant buttons. They just take space you could use to see web pages. So, why don’t you spend a few minutes cleaning it up so that you can get the most of it?

If you share your desktop, occassionally require a big set of Firefox extensions or use your browser for various, accurate applications, you should consider using multiple profiles.