Does this occur while you are working within the same page, or when you use the Back button? For the Back button problem, please see this thread: [https://support.mozilla.org/questions/1019567 Firefox 32 always gives "Document expired" every single time I hit the Back key to return to search results.] For other situations, could you try the steps in this thread: [https://support.mozilla.org/questions/1026968 I keep getting a "Your Session has expired or cannot be retrieved. Please click below to log back in and try again." when I try to use Cisco netacad.] Do either of those help?