function getXMLHttp()
{
   var XMLHttp = null;
   if (window.XMLHttpRequest)
   {
      try
      {
         XMLHttp = new XMLHttpRequest();
      }
      catch (e)
      {
      }
   }
   else if (window.ActiveXObject)
        {
            try
            {
               XMLHttp = new ActiveXObject("MSXML2.XMLHTTP");
            }
            catch (e)
            {
               try
               {
                  XMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
               }
               catch (e)
               {
               }
            }
        }
   return XMLHttp;
}