Mac Forums

I was watching a vid on youtube and a guy was saying the 1st things you should do when you have a new mac. Well, I went into systems pref (like he said) and I pressed "detect displays" and all HELL has broken loose!!!! My screen is so freaking screwed-up I can barely use my comp now!!! I tried everything I could think of to make it go back to normal and Nothing has worked!!!! Someone Please Help Me!!!!!!!!!