çözünürlüğe göre değişen arkaplan yapmam lazım

<script language='javascript'>
deger1=screen.width
deger2=screen.height
deger3=(deger1+'x'+deger2);
switch(deger3)
{	case '1280x800': document.write('<style>body{background-color:#111111;}</style>');break;
	case '1024x768': document.write('<style>body{background-color:#222222;}</style>');break;
	case  '800x600': document.write('<style>body{background-color:#333333;}</style>');break;
default: break;}
</script>