answer:Most websites use cookies to store user data to authenticate the user (or at least cookies to store what session you are using on the server). All cookies expire after a certain time period, depending on what they set that time to, maybe a week, a month, after the browser closes etc. Either you haven’t visited the site recently enough, or perhaps you or someone else is clearing out your history, which a lot of times can clear cookies. That would require you to have to log back in. Finally I have heard of some anti-virus software clears cookies for various reasons. I can neither confirm nor deny this, but I could see how many would do that due to many consumers think cookies are bad for your computer when they are not, they are essential for modern web pages. Overall, check your browser settings to ensure its not clearing your history, or automatically removing cookies for some various reason.