Firefox 3 stores its session data in a JavaScript file located in the user profile folder. To restore an accidentally discarded session, simply:
- Quit Firefox.
- Replace the current JavaScript file with the backed-up version.
- Restart Firefox.
—Jesse Kirdahy-Scalia (13 September 2009). "Restore a Lost or Discarded Firefox Session in Three Quick Steps". Open Media Boston. Media Working Group, Inc.