A must have add on which clears the browser history instantly. A reinstall of Firefox 29 beta said that it was not compatible, but certainly is with ALL Firefox releases & reinstalled from the add on page
While easier (shortcut) than using the link in the menu, note that it does not clear out cookies (and perhaps other features you may have chosen in the "Clear All History" pannel), but probably only browsing history. You may be fooled to believe they are gone but they aren't! Check it out in the Preferences after clearing history.
The purpose is mainly to add the shortcut "clear history" in the history menu (where it belongs in my opinion). The shortcut removes the history without prompting you, which is not the case with Ctrl+Shift+Del.
The 'Clear History' function is so essential to Firefox, I was shocked not to find it upon downloading Firefox 3.5.1. Anyway, this add-on is extremely satisfactory. It clears all your history in a snap. You'll be very pleased with it (especially guys..y'know what I mean..)!