function popup(popupUrl,w,h) {
     var winl = (screen.width - w) / 2;
     var wint = (screen.height - h) / 2;
     var winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+'resizable=0,scrollbars=1';
	 var w = window.open(popupUrl, "site_popup", winprops);
	 w.focus();
}