This annoyed me simply too much. It actually made me startup a wordpress blog where I can post my own personal tips – mostly for myself, just to remember!
Everytime I started writing an url, firefox came up with several suggestion based upon history and bookmarks. This got to stop!
Goto: about:config, find browser.urlbar.maxRichResults and set value to 0.
Nomore autosuggestions in the urlbar.