CTRL-ENTER in Firefox
One tenth of the web sites I often visit are having the domain names in the format of www.xxx.com. In Firefox, I can just key in the middle part xxx and then press ctrl-enter. Firefox will add www and com and place xxx in between. For instance, I type blogger in the navigation bar follow by ctrl-enter, it will bring me to www.blogger.com. This is quite a handy feature. It saves me a lot of time.