AutoAuth automatically submits HTTP authentication dialogs when you’ve chosen to have the browser save your login information. (If you’ve already told the browser what your username and password are, and you’ve told it to remember that username and password, why not just have it automatically submit it instead of asking you each time?)

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.]