First, does it happen in all screen angles? Does it work OK with an external monitor. If with an external monitor there are no issues, you need to check your LCD screen.
First open up the case (check online for steps for your model) to get to the LCD screen connections, reseat them. If that did not fix it, start with replacing the inverter.
http://www.pchub.com/uph/content/fq2_dis_lcd_inverter.html
Then you are probably left with replacing the LCD pannel. You may be able to find the whole LCD assmebly with the lid on ebay, easier than taking the LCD out of the lid. If you can't do the work yourself, generally with the labor costs, you are better off buying a new laptop unless yours is only a few years old and was over $600 or so when new.