/* generieke popup functie	*/	
function popup(url,breedte,hoogte)	{
	var width, height;
	if (document.all)
	    height = document.body.offsetHeight, width = document.body.offsetWidth;
	else if (document.layers)
	    height = window.innerHeight, width = window.innerWidth;
		
	var y = (height/4)-0, x = (width/4)-0;
	
	popupvenster = window.open(url,"venster","width="+breedte+",height="+hoogte+",toolbar=0,scrollbars=no,directories=0,status=0,menubar=0,location=0,resizable=0,top=" + y + ",screenY=" + y + ",left=" + x + ",screenX=" + x);

}