You have a backup of all these files in a safe location? Good.

This has gotten a little more complicated in Firefox 33. The file that Firefox will look for at startup is still called sessionstore.js. However, while you are running Firefox, it is updating those other files, and it seems that sessionstore.js is written out when Firefox exits.

Thus, you need to remove sessionstore.js (you can rename it to sessionstore.old) before starting up Firefox so it looks in the sessionstore-backups folder for the files you have restored there.

Does that make sense?

Or you could rename your most promising file as sessionstore.js so that Firefox reads that file at startup. Please only make the switch with Firefox fully shut down.

Thank you for your reply. I changed the name of the promising file (which has the desired yesterday's date on it) to sessionstore.js but the newer session of tabs opened. I think the old file is still ok but just not being opened.

It seems as if Firefox does not want to open that file. (It was not in the folder before... as i said, just *.bak and the 2 js files ("recover" and "previous").

I opened Firefox after the file had been renamed to sessionstore and got homepage. Then I went to History and Restore session. Is there another way to get Firefox to open sessionstore.js file?

Should I only have the desired sessionstore.js file in the sessionstorebackups folder? Could that be the problem (I have other files that have been renamed in it but don't think Firefox would open them?)

Thanks again.

The sessionstore.js file is in the profile folder at the main level, not in the sessionstore-backups folder. Since this just got revamped in Firefox 33, I'm not 100% certain, but I believe that is where Firefox will look for the file. After exiting Firefox and renaming the (small, useless) sessionstore.js file to sessionstore.old, try moving the (promising) sessionstore.js file into the main profile folder right next to sessionstore.old.