function open_window(page) {
	var height=500;
	var top = (screen.height - height) / 3;
	var width=688;
	var left = (screen.width - width) / 2;
	pop_up = window.open(page,"VirtualTour","menubar=no,toolbar=no,status=no,scrollbars=no,resizable=yes,height="+height+",width="+width+",top="+top+",left="+left);
}