Hi,

You should be able to select the entry you want to remove with the up/down arrow keys and then remove it by pressing Delete. For reference, see Control whether Firefox automatically fills in forms.

AHA! I'd been told to select the item to remove in the past, but never using the arrow keys. Thanx! Not to be greedy, but is there a way to move an entry up or down in the list? I'd like to be able to alphabetize a list to make it easier to find things.

I don't think it can be sorted. There's some kind of algorithmic magic under the hood to prioritize most popular entries.