AutoAuth automatically submits HTTP authentication dialogs when you’ve chosen to have the browser save your login information.
About this Add-on
If you don't have a username and password saved for a subdomain (e.g., foo.bar.com), AutoAuth will give you a list of suggestions for that domain, based on other saved usernames and passwords for similar subdomains (e.g., bar.com or *.bar.com). Just choose which username to use from the list, and hit the Autofill button. [This feature is only available in Firefox 2.]