This is aparently the intended behaviour in Firefox 4, note you will normally still have the option to restore tabs. You can change the behaviour so it is similar to firefox 3.6 see for instance this post

One of the changes in Firefox 4: by default Firefox 4 does not display the "Save Tabs and Exit" warning message when closing multiple tabs, but it can be turned back on by changing some preferences.

• Saving tabs was not removed from Firefox 4, but it works a bit differently.
  • By default, Firefox 4 will not ask to save tabs, but instead it will always save your tabs on exit. You can restore them next time by choosing "Restore Previous Session" from the History menu, or pressing the restore button on Firefox's default home page.
  • Note: This was a decision by the developers. On this forum, we are all uncompensated volunteers here to help other users. The developes/employees of Mozilla/Firefox rarely, if ever visit here.

Browsing history must be saved

• Firefox button: Firefox button > Options > Options > Privacy > [X] Remember my browsing history
• Menu Bar: Tools > Options > Privacy > [X] Remember my browsing history

Also make sure you do not clear "Browsing History" when using Clear Recent History or when closing Firefox

• Using Clear Recent History
  • Firefox button: Firefox button > History >Clear Recent History
  • Menu Bar: Tools > Clear Recent History
• When closing Firefox
  • Firefox button: Firefox button > Options > Options > Privacy (checked) > Settings
  • Menu Bar: Tools > Options > Privacy (checked) > Settings
• See: https://support.mozilla.com/en-US/kb/Clear%20Recent%20History

To display the "Save Tabs and Exit" message when closing multiple tabs, you can do the following:

1. Type about:config in the URL/Location/Address bar and press the Enter key
2. Accept the warning message (promise to be careful)
3. The preferences page/list will open
4. Filter = browser.tabs.warnOnClose
5. If its value is set to false, double-click on it (in the lower panel) to toggle its value to true
6. Repeat steps 4 and 5 for these following 3 preferences also:
   • browser.warnOnQuit
   • browser.warnOnRestart
   • browser.showQuitWarning
     • Note: last pref is new in Firefox 4b12, may need to add (boolean)
     • Info/Instruction for using about:config: http://kb.mozillazine.org/About:config
7. See:
   • https://support.mozilla.com/en-US/questions/785169
   • http://forums.mozillazine.org/viewtopic.php?f=23&t=2105039&p=10434467&sid=fd2a35945bb2c633687f7b50d8c53989
   • http://blog.zpao.com/post/3174360617/about-that-quit-dialog

Absolutely brilliant. Followed your guidance and all now working as before. Shame the troubleshooting guide wasn't as useful! Thanks very much for your help

You are welcome, AcePilot.

Brilliant! Thanks a bundle. Did exactly as you described, now back to how I like it - you're a star...!

I followed the above advice, but it doesn't work. I had 4.0 installed and was a nightmare to deal with. I uninstalled it, then loaded 3.5, hoping that would be easier to deal with. It is, in certain circumstances, but I still can't get a new tab to default to my home page search engine. I'm at my wit's end!

"I still can't get a new tab to default to my home page search engine"

That is not the topic of the original poster's question. Please post a new question of your own.

Stop posting in threads that do not apply to the problem you are experiencing; in addition to this thread, for your off-topic posts, see:

• https://support.mozilla.com/en-US/questions/805743/edit/173345
• https://support.mozilla.com/en-US/questions/804483#answer-173019