I was more than excited to install a new version of firefox when I heard that they already released the community - driven development of the fourth version (firefox 4). After quite some time of enjoyment with the browser's graphics and ergonomics, I found out that they DID NOT enable the window prompt to SAVE TABS. When you close the browser, all you get is a notification to CONFIRM that you are really closing the tabs.
For me this is a great BOO-HOO! I live with my tabs; When I close the browser I want to see them again the next time I open it. Good thing I found a relatively good (but not user - friendly) solution and it goes like this:
Step 1: Type about:config in the address bar. Click "I'll be careful, I promise!" button.
Step 2: Type browser.showQuitWarning in the filter tab that you will see. This will show you one row of result of browser.showQuitWarning set to false.