Why are my laptop keys functioning like theyre continuously being pressed?

They're not dirty or sticky and they pop back up fine, but when i'm playing a flash game or whatever and i press the directional arrows or wasd to move every now and again the player will continuosly move right left duck or jump even though my fingers off the button. I don't know what the problem is it's been doing it since i got it. Never spilled anything on it. Help?