If you take advantage of Firefox’s ability to save passwords and prefill them on certain web pages, eventually you will have a bunch of dead or out of date entries. It is good idea to occasionally review and clean them out. Here is how (Firefox 3):

  1. Go to Tools > Options.
  2. Security tab > click Saved Passwords.
  3. Click Show Passwords. It is good to show the passwords in the event you have multiple entries and some are not correct.
  4. Highlight and remove the dead entries.

That’s it. While keeping your saved passwords list clean isn’t going to give you a performance increase, it is overall good maintenance to perform on your Firefox browser.