how come it just go's half black an half white??????

[shooter7]

hello every1 can any1 tell me y it is wen i want 2 click on full screen of say youtube or simaler thing, all i get is 1half of my screen go's black n other half go's white.
i can still here the sound of the link but 2triangles on my screen. can see full screen on
my dvd player but not wen i view things of say the web. can any1 help??x