Do you mean two thirds of the screen is blank, or it looks like the screen is zoomed in ?
If zoomed in then try double-tapping the screen with 3 fingers and then turn Setttings > General > Accessibility > Zoom 'off'.
If two thirds is blank then have you tried a reset to see if that fixes it ? Press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.
Thanks I did mean the screen has gone dark on two thirds sometimes you can see through it for a few seconds but it is unuseable I have tried the reboot. Took it to a apple store today and they put it back to factory settings, but came out none the wiser and all they said was that it would cost £169.99 plus vat to fix, it's not even 2 years old. I hoping someone might have had the same problem but with a cheaper solution.
I have an Ipad 1 gen bought in 2010. Doing some research I think there is a connection between date bought and the screens. Thick striped, black white or colored but Apple are refusing to acknowledge. If I can get enough people I will take this further if I can! Please join me on Facebook @Apple Ipad screen issues Thanks!