Laptop sreen

most likely the pcb at the top of the screen has a loose connection.
try www.rolta.co.uk for a new screen.
 
Happens at certain situations?
Model of laptop?
Tech specs?
Ambient temps?
Cooling fan gets noticibly louder?
Tested temps?
 
Loose connector at screen or damaged ribbon cable for the display. You could plug in an external display if your laptop has the provision for it. It may require that you depress a specific function key as well to get the external display to get a signal from the laptop.