If you are not in a private browsing session, you can exit Firefox, then when you start Firefox again, go to the History menu and choose Restore Previous Session. To Exit, use either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Note: The Flash installer sometimes restarts Firefox automatically with an advertising page. In that case, check the History menu immediately for Restore Previous Session, don't close the advertising page first, or your previous session will get erased.

This can also help,

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