--> To keep tabs,right click on each one then Pin Tab.

Does Firefox create a new sessionstore.js file in the Firefox profile folder (i.e. the file has a current time stamp)? You can check for problems with the sessionstore files (sessionstore.js) files in the profile folder that store session data. You can use this button to go to the currently used Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox *http://kb.mozillazine.org/Multiple_profile_files_created Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible). Current Firefox versions also keep backups in the sessionstore-backups folder.