NotAwesomeBar is an experimental Firefox extension capable of preventing those web sites you’ll rather prefer not to appear on Firefox’s AwesomeBar from doing so.
All you have to do is install the add-on, restart Firefox, thence each time you do a bookmark simply check the “Hide from AwesomeBar Searches” now found on the bookmark dialog box and that web site won’t show up on the AwesomeBar.
You can also retroactively deal with “older” bookmarks. Right-click on them, take “Properties” and drop the “NotAwesome” tag into the Tags field and “Save”. Use the Bookmark Manager if you have several “notawesome” bookmarks to fix.
NotAwesome is still in the experimental stage. It works on Firefox 3.0 and higher version.