function createXMLHTTP() 
{
   var ajax;
   try 
   {
      ajax = new ActiveXObject("Microsoft.XMLHTTP");
   } 
   catch(e) 
   {
      try 
      {
         ajax = new ActiveXObject("Msxml2.XMLHTTP");
         alert(ajax);
      }
      catch(ex) 
         {
         try 
         {
            ajax = new XMLHttpRequest();
         }
         catch(exc) 
         {
            alert("Esse browser não tem recursos para uso do Ajax");
            ajax = null;
         }
      }
      return ajax;
   }
   
   var arrSignatures = ["MSXML2.XMLHTTP.5.0", "MSXML2.XMLHTTP.4.0",
   "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP",
   "Microsoft.XMLHTTP"];
   for (var i=0; i < arrSignatures.length; i++) 
   {
      try 
      {
      var oRequest = new ActiveXObject(arrSignatures[i]);
      return oRequest;
      } 
      catch (oError) 
      {
      }
      throw new Error("MSXML is not installed on your system.");
   }
}