App tabs and Tab Groups (Panorama) are stored as part of the session data in the file sessionstore.js in the Firefox Profile Folder

• http://kb.mozillazine.org/Session_Restore

Make sure that you do not use Delete browsing, search and download history on Firefox to clear the "Browsing History" when Firefox is closed because that prevails and prevents Firefox from opening tabs from the previous session.

It is also possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Profile Folder

Delete (or rename) sessionstore.js and sessionstore.bak in the Profile Folder

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

If you see files sessionstore-##.js with a number in the left part of the name like sessionstore-1.js then delete those as well.

Deleting sessionstore.js will cause App Tabs and Tab Groups to get lost, so you will have to create them again (make a note).

See:

• http://kb.mozillazine.org/Session_Restore

While this is a resolved thread the App Tab pinning SHOULD NOT be session controlled, they should be application saved and not be removed unless one actually removed them manually.

This needs to be fixed in a future update of Firefox 4

@gwmbox

Feel free to file a Bug report and submit a patch to change where that data is stored - if you think you have a better to store that data.

Sorry, sounds great but maybe your file location is for Windows. I'm on a Mac and can't find the file you're talking about. Haven't learned much about the nuts and bolts. A search yields nothing and I can't find it when I look in various folders. Help doesn't help. Any suggestions for this ignorant person?

If you can't locate the Firefox Profile Folder then use this button:

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

I don't see a button, but I went to your "Firefox Profile Folder" link again and reread it. Then looked again. I found the files! They are under the other user account that I inadvertently created when I loaded my laptop onto this machine. That's another story for another thread. The app tabs are working now-- to be honest, they had started working days ago, though I don't know why or how. I moved the sessionstore.js and Firefix opened without my tabs, then replaced it and opened it again, and it came up with my tabs. Not sure at this point what value it has, but it was cool. Thanks. Maybe I'll post a plea for help with merging my two user accounts.

I am in Firefox 5.0 and having the same problem. Have deleted all the sessionstore (js) and (bak) files with no effect to the system. I like the app tab concept, but adding them at each session is becoming a little tedious.