I just installed Yosemite on my mini. The Apple toolbar at the top of the screen keeps disappearing when I maximize a window. That didn't happen when I had Mavericks. It is very frustrating to move the mouse cursor to the top of the screen to see the toolbar. As soon as I move the mouse away, the toolbar disappears. I've looked around System Preferences & I don't see any way to keep the toolbar locked to the top of the screen when I maximize a window. I've had to add Mission Control to the Dock so I can change windows. I also have to move the cursor to the bottom of the screen to show the Dock because that disappears too. HELP! How do I lock the Dock to keep it from disappearing & how do I lock the Apple toolbar so that it doesn't disappear every time that I maximize a window?