Few things are as frustrating as trying to start your Mac only to end up with the dreaded Mac folder with a question mark. You've probably tried using keyboard shortcuts like CTRL + R, CTRL + Option + R, or Shift + CTRL + Option + R, but you still get the flashing folder icon on startup.While this may strike fear into your heart as a Mac user, there are known causes for it and proven solutions that will help you get your Mac back on track.