As Brain said. It is almost certain to be a harware issue; lose cable or damaged display chips.
If you haven't done so you cna try a reset (hold down the home and power button until the Apple logo appears), but if that doesn't fix it, then there's nothing else you can do except take it to Apple or another (certified) repair center and get their oppinion.
Or, you can try fixing it. Yourself. Decdent instructions can be found at the ifixit.com site. But be warned, this takes some basic tech skills, a lot of patience, and the abiltiy to follow instrucions to the T; with no guarnateed results.
I've never felt the urge to try it myself. Or to be more precise, I've never had a broken iPad that I thought was worth the trouble.