If you are liked to the way Firefox 3 prompted to save open tabs on exit you’ll be surprised when Firefox 4 doesn’t ask by default. The feature isn’t missing, it’s just turned off. Follow the steps below to turn this feature on.
Please note: This solution was posted by TonyE on the Mozilla support forums. I am not taking credit, just passing it along.
- Open Firefox 4.
- Type about:config into the location bar and press enter.
- Accept the warning message that appears, you will be taken to a list of preferences.
- Locate the preference browser.tabs.warnOnClose, if its value is set to false, double-click on it to change its value to true.
- Repeat this for these 2 preferences browser.warnOnQuit, browser.warnOnRestart.
- There is one more preference that needs to be set to true – browser.showQuitWarning.