I exited firefox, and after two hours I opened it again to find that I have lost all my tabs from the previous session. I tried to follow of one of your online support process to recover my tabs but I couldnt find the file upgrade.js-build_id in the folder sessionstore-backups. I also tried to restore a previous version of these files using the properties window, but there was not any previous versions for the files recovery.js, recovery.bak, and previous.js. BTW, I changed the setting of windows so that it shows all the hidden files. So how may I do to recover my lost tabs?