Opera uses the entire screen to show contents of a page and doesn’t waste a single pixel on the screen for displaying anything else. This is definitely great for stretching the space available for viewing a particular website but might get less practical when you decide to spend the rest of your surfing life in fullscreen rather than normal mode with all toolbars and stuff around the page itself or if you at least intend to make better use of the fullscreen feature.
I’ve always thought highly of surfing in fullscreen which is in some way more comfortable. Besides, using Windows’ cool-switch feature ensures ease of switching to other apps w/o any problems. However, there had always been a drawback making me put this feature aside a bit. The thing is that Opera with enabled tabbed browsing won’t display the tabs panel when in fullscreen mode, making it quite confusing and more difficult to keep order in websites you have open in all those tabs and control the amount of active tabs. Fortunately, there’s a rather simple way to resolve this problem.
You can easily force Opera to display various bars in fullscreen by editing the action taking place after pressing the F11 key. To do this, you’ll have to open the Advanced tab in Preferences window (Ctrl+F12) and continue to the Shortcuts menu. Here, you can edit the default keyboard layout. In the editing dialog, paste the string “Platform Windows-Unix-MCE, F11″ into the search field and double-click on the right side of the appropriate line. Now you can add a short statement to achieve desired result:

