I recently discovered that there's a very simple way to remove saved form entreis you dont need. I frequently enter the wrong username in login forms, or mis-spell something and want rid of those erroneous values.

To do so is simple: click in the offending input field, use the arrow cursors to scroll down to theentry to be deleted, hold hown your Shift key and press Delete.

Source: Thanks to the Man in Blue(external link) for this handy tip.