It allows you to erase your browser history/cookies for 5 minutes, 2 hours, or 1 day, in case you want your browser to be able to unsee wherever it is that you've blundered into. Read the rest

http://feeds.boingboing.net/~r/boingboing/iBag/~3/FdXEB5i-OZk/new-firefox-has-a-forget-b.html