You close the browser window inadvertently with the click of a mouse whereas you just wanted to maximize it. Can the previously opened websites be restored quickly?

The function for re-constructing recently closed tabs is available for a long time now. However, Firefox 3.5 can also fetch back the contents of the closed window. For that, open 'History I Recently Closed Windows'. The last closed windows are available for selection in the menu, which have been marked with the help of the first tab. Since you normally need the function only when you have just closed a window, the first entry of the list should be the right window. Clicking it restores the previous status. It goes much faster with the [Ctrl]+[Shift]+[N] keyboard shortcut.

NOTE: the normal History helps you further in the older versions. The History can be displayed in the sidebar with the [Ctrl]+[H] shortcut or via the menu. You will find all the visited websites arranged chronologically here. However, you must find out on your own, which the last closed Internet addresses were.