// change_alpha():
// aendert die Opacity eines Elements (id) zum Uebergebenen Wert.
// z.B. value = 50

function change_alpha(id, value){
	var el = document.getElementById(id);
	
	el.style.filter="Alpha(opacity=" + value + ")";
	el.style.opacity = value / 100;
	el.style.MozOpacity = value / 100;	
	
}