/* generieke popup functie	*/	
function popup(url,hoogte,breedte)	{
	var height, width;
	if (document.all)
	    height = document.body.offsetHeight, width = document.body.offsetWidth;
	else if (document.layers)
	    height = window.innerHeight, width = window.innerWidth;
		
	var y = (height/2)-(hoogte/2), x = (width/2)-(breedte/2);
	
	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);

}