It may have something to do with cookies.
"
HTTP cookies, sometimes known as
web cookies or just
cookies, are parcels of text sent by a
server to a
web browser and then sent back unchanged by the browser each time it accesses that server.
HTTP cookies are used for
authenticating, tracking, and maintaining specific information about users, such as site preferences and the contents of their
electronic shopping carts."
Not entirely sure what you should do to sort it out but I'm pretty sure cookies play a part! (Yum, cookies.)