Constantly typing www. and .com in the address bar is a tedious job. For www., just type the domain name and press Ctrl + Enter. For www., just type the domain name and press Shift + Enter. Firefox will automatically fill-in those up for you.
The same goes with sub-pages. Say you’d like to go to our Firefox tips. Just type apple/trailers and press Ctrl + Enter (since it’s a .com) and Firefox will fill in the www. and .com for you pointing you to www.apple.com/trailers. A few more keystrokes saved.
Via Lifehacker