For Firefox 3.5 users, this add-on is no longer needed, so installing it will just change a built in Firefox 3.5 preference to only search visited history pages and uninstall itself. See the following page for more info:
http://ed.agadak.net/2009/02/firefox-31-location-bar-privacy
Hide pages (bookmarks) that you haven't visited from showing in the AwesomeBar. This is for users that don't want to see any bookmarks showing up unless they've used the bookmark since deleting certain pages/sites or clearing the history.