If you occasionally type URL directly into the address bar of your browser, you know it's kind of a pain to do manually since you need to use the mouse and highlight the entire existing address before you can get rid of it. But there is an easier way if you are using Firefox... two of them actually. Just type either Control + L or hit the F6 key. If you do either of these things, the URL in the address bar will be highlighted and the address bar will have the focus so you can just start typing in a new URL.