restore old tabs from version 3 over to version 4
Any upgrades should have restored old tabs. In v3.x I could restore old tabs by renaming the backup. After upgrading to v4.x I can't find a solution to restore. Until a solution is found, I'm not using FF fearing any backups would be overwritten.
Wšykne wótegrona (1)
Firefox 4 still uses sessionstore.js to store the current session, but now also saves a copy in sessionstore.bak on each start that you can open via Firefox > History > Restore Previous Session.