What are the key combinations to fix a flipped screen?

As my computer was falling, I grabbed it to prevent it from hitting the ground. However, when I grabbed it, I hit some keys. The screen turned black, and than it reappeared... on it's side.

This situation has happened to this computer more than once; the screen was flipped upside down last time, and now is flipped on it's side, so that the Google bar appears vertical on the left side of the screen (if you were to view the screen from the normal perspective).

So, are their any computer experts that know how to get it back? (if needed information, my laptops' maker is Dell)