function openInfoWindow(marker, id) {
  marker.openInfoWindowHtml("Loading details...");
  var request = GXmlHttp.create();
  request.open("GET", "/community/ajax/tagdetails.ashx?id="+id, true);
  request.onreadystatechange = function() {  
    if (request.readyState == 4) { 
      marker.openInfoWindowHtml(request.responseText) 
    }
  }
  request.send(null);
}