function getBrowserSize (id) {
	var width = "auto";
	var height = "auto";

	if (window.innerWidth && window.innerHeight) {
		height = window.innerHeight;
		width = window.innerWidth;
	}
	else if (document.body.offSetWidth && document.body.offSetHeight) {
		height = document.body.offSetHeight;
		width = document.body.offSetWidth;
	}
	
	
	if (width > 1024) {
		document.getElementById('Content').style.background = "url('bilder/rock.jpg') bottom";
	}
	else if (width <= 1024 && width >= 800 ) {
		document.getElementById('Content').style.background = "url('bilder/revolution1000x665.jpg') bottom";
	}
	else if (width <= 800 && width >= 640) {
		document.getElementById('Content').style.background = "url('bilder/rock800x533.jpg') bottom";
	}
	else {
		document.getElementById('Content').style.background = "url('bilder/rock640x426.jpg') bottom";
	}
}

window.onresize = getBrowserSize;