clipped from: lifehacker.com 
You sit down at a computer running that other browser and you hit Ctrl+T to open a new tab, and... nothing happens. Ctrl+T! Ctrl+T! You mash the keyboard and gnash your teeth and finally, begrudgingly, reach for the mouse. Anyone who's burned keyboard shortcuts into their muscle memory knows it can feel like you're missing a limb when they're not available. But when it comes to Firefox—which is loaded with key combos—we want to know:
Ctrl+T (New tab) |
Ctrl+L (Cursor to address bar) |
Ctrl+K (Cursor to search box) |
Ctrl+Shift+T (Undo last closed tab) |
Ctrl+ -/+ (Reduce/enlarge font size) |
F5 (Reload current page) |
Ctrl+Enter (add http://www and .com to word in URL bar) |
Ctrl+F (Find as you type search box) |
Other--list it in the comments! |
(Mac users, substitute the Cmd key for Ctrl.)