My asus screen wont get any single

hey guys , i was on my asus desktop that iv bought only 1 month ago and on the keyboard there was a moon key. I didn't know what it was so i pressed it. suddenly the computer screen went off and so did they keyboard but not the mouse or the monitor. i rebooted the monitor and everythings working fine but the screen is getting no single ... i replugged the plugs and everything but it's still getting no single! someone help me plz ....!