var XMLHttpFactories = [
   function () {return new XMLHttpRequest()},
   function () {return new ActiveXObject("Msxml2.XMLHTTP")},
   function () {return new ActiveXObject("Msxml3.XMLHTTP")},
   function () {return new ActiveXObject("Microsoft.XMLHTTP")}
];

function createXMLHTTPObject() {
   var xmlhttp = false;
   for (var i=0; i<XMLHttpFactories.length; i++) {
      try {
         xmlhttp = XMLHttpFactories[i]();
      }
      catch(e) {
         continue;
      }
      break;
   }
   return xmlhttp;
}

function sendRequest(url, callback, postData) {
   var req = createXMLHTTPObject();
   if (!req) return;
   var method = (postData) ? "POST" : "GET";
   req.open(method,url,true);
   req.setRequestHeader('User-Agent','XMLHTTP');
   if (postData) req.setRequestHeader('Content-type','application/x-www-form-urlencoded');
   req.onreadystatechange = function () {
      if (req.readyState != 4) return;
      if (req.status != 200 && req.status !=304) {
         //alert('HTTP error ' + req.status);
         return;
      }
      callback(req);
   }
   if (req.readyState == 4) return;
   req.send(postData);
}