var popupWindow = null;
function popup(url, width, height) {
	if (popupWindow != null) {
		if (!popupWindow.closed) {
			popupWindow.close();
		}
	}

	var top  = ($(document).height()-height)/2;
	var left = (($(document).width()-width)/2)-13;
	var options = "resizable=no,toolbar=no,location=no,scrollbars=no,menubar=no,status=no,width="+width+",height="+height+",top="+top+",left="+left;

	popupWindow = window.open(url, "popup", options);
	popupWindow.focus();
}