var stylesheet, hoehe;

if (window.innerHeight) {
 hoehe = window.innerHeight;
} else {
 hoehe = document.body.clientHeight;
}

if (hoehe<=508) {
 stylesheet = 'size1.css'
}
else if (hoehe<=630) {
 stylesheet = 'size2.css';
}
else if (hoehe<=840) {
 stylesheet = 'size3.css';
}
else if (hoehe<=1080) {
 stylesheet = 'size4.css';
}
else {
 stylesheet = 'size5.css';
}

document.writeln('<style type="text/css" media="screen"><!-- @import url(' + stylesheet + '); --> </style>');

// Zum Umschalten per Link
function demo(x, y) {
 window.resizeTo(x, y);
 location.reload();
}