function resizebg(){  
	var leftbg = document.getElementById("leftbg");  
	var rightbg = document.getElementById("rightbg");
	var bodyparentheight = document.body.parentNode.scrollHeight;  
	var bodyheight = document.body.scrollHeight;  	
	var htmlheight = (bodyheight>bodyparentheight) ? bodyheight : bodyparentheight;
	var windowheight = (window.innerHeight) ? window.innerHeight : document.body.clientHeight;  
	//alert('body: ' + bodyheight +'\r\nparent: ' + bodyparentheight +'\r\nwindow: ' + windowheight);
	if ( htmlheight < windowheight ) { 
		document.body.style.height = windowheight + "px"; 
		leftbg.style.height = windowheight + "px"; 
		rightbg.style.height = windowheight + "px"; 
		document.getElementById("content").style.height = windowheight-160 +"px";
	}  else { 
		document.body.style.height = htmlheight + "px"; 
		leftbg.style.height = htmlheight + "px";
		rightbg.style.height = htmlheight + "px";
		document.getElementById("content").style.height = htmlheight-160 +"px";
	}  
} 

//====================== Aanroep functies bij Onload-event
window.onload = function() {
	resizebg();	
}

//====================== Aanroep functies bij Onresize-event
window.onresize = function() {
	resizebg();
}