function run_popup(url) {
	popwidth = 434;
	popheight = 334;
	window.open(url,"pop_up","width="+ popwidth +",height="+ popheight +",scrollbars=yes,toolbar=no,resizable=no," + align_string_pop(popwidth, popheight))
}


function align_string_pop(popwidth, popheight) {
	var breedte = screen.width;
	var hoogte 	= screen.height;
	
	var prop_left 	= (screen.width/2) - (popwidth/2);
	var prop_top	= (screen.height/2) - (popheight/2);
	
	return "left=" + prop_left + ",top=" + prop_top;
}