The autocomplete portion of a browser only causes the "letters" to be transferred over but when a password is saved, it's actually save in a cookie, which then "allows" the user to be logged in over and over.. Still, most websites have a limit as to how long the cookie will be "good".. After a time, the website requires a new cookie or a new login to gain access. Or it's possible the cookie is being deleted, at which time a new login would be required to create the cookie again. It's also possible the user has set the option to delete all cookies when the browser is closed?
Hope this helps.
Recently I have a problem with a users XP Pro, IE7 and autocomplete. Usually after they've enetered the information username and password, it automatically logs them into the website when they come back to it. After about two months this stops and they have to reenter the username and password. The username will appear in the list of autocomplete options its just not logged in like it usually is. Any ideas how I can fix this? Is there an option that makes this expire or something of that sort?