window.onload = function(){
	var headerH = document.getElementById("header").offsetHeight;
	var footerH = document.getElementById("footer").offsetHeight;
	var grailH = document.getElementById("maincontent").offsetHeight;
	var windowH = window.innerHeight;
	if (windowH == undefined){ // IE kenn inner Height nicht 
		windowH = document.body.clientHeight;
	}
	targetH = windowH -footerH -headerH;
	if(targetH >grailH){
		document.getElementById("maincontent").style.height=targetH+"px";
	}
	
	init_zoom();
};