Firefox would normally ask to update the stored password if you have let Firefox fill the old password and have edited (removed) that password to enter the new correct password. If this didn't happen the you can remove the password in the Password Manager and let Firefox ask again to save the new name and password. *Tools > Options > Security: Passwords: "Saved Passwords" > "Show Passwords" Note that websites may be using autocomplete=off to prevent Firefox from saving the name and password. You can remove autocomplete=off with a bookmarklet to make Firefox store form data like names and passwords. *http://kb.mozillazine.org/User_name_and_password_not_remembered Note that Firefox won't auto-fill a saved name automatically when autocomplete=off is used, so you need to double-click the empty name field to get a drop-down list.