Firefox treats pinned tabs differently than start pages. You can't set a pinned tab as a start/home page but you can set Firefox to open all of your tabs and windows from last time. If you do that (sounds like that's what you are doing), Firefox will load whatever tab you were using last. If it's that app tab then that's what will load. If it's another tab, then that one will load. Does that make sense?

Ok, thanks. That's fine, but that also means if I do want Ff to open to one of my pinned tabs then I have to make sure that is the last page I was on before I exit out of Ff. Oh well. Do you know if pinned tabs will be able to open on start pages in the future? Thanks.

If you close Firefox with a pinned tab selected and you have at least one regular tab then Firefox should select that pinned tab on a next start if you reopen the tabs automatically via Show my windows and tabs from last time.

I close Firefox with 2 pinned tabs and some variable number of regular tabs. When I open Firefox the next time, the two tabs previously pinned are unpinned.

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

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the 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).