Firefox has really pissed me off(to go off topic for a bit, sorry, Frank). Since v.3.0 FF has removed your ability to remove your visited websites, delete your history and to have any control over your browsing details after they've been browsed.
From about 1 to 2 months ago, I've used Google Chrome as an alternative and, I must say, it is really functional and pliable to your needs. Mozilla have taken a turn for the worst since FF v.2.xx(which was a fantastic browser), everything after 3.0 is taking away your right to control your browsing details. Even the history/clear private data/etc. items do not work anymore in FF 3. Google this for more info. It isn't just me...