Ubuntu Unity, once you get use to it, can be neat to use. It offers great new features that are easier to use. One of the new feature is the menu bar, or commonly called global menu bar. This
Macintosh way to display the menu for each windows might be annoying if you are not use to it (or never used a Mac before).
To restore the menu bar to its window, simple run this command from the terminal:
sudo apt-get autoremove appmenu-gtk appmenu-gtk3 appmenu-qt
Now, close all your apps and open them again. The menu bar is back the way you like it!
Firefox won't probably be affected with this command. To disable it simply go to
Tools -> Add-Ons and then disable the Global Menu Bar Integration extension. Restart firefox et voilà!
If by any reason you want to enable this global menu, you can do it by running the following command:
sudo apt-get install appmenu-gtk appmenu-gtk3 appmenu-qt
If you prefer not to uninstall the package, you can change the settings instead:
gsettings set com.canonical.desktop.interface scrollbar-mode normal
To enable it:
gsettings reset com.canonical.desktop.interface scrollbar-mode