function createRequest() {
  var request = null;
  try {
    request = new XMLHttpRequest();
  } catch (trymicrosoft) {
    try { 
      request = new ActiveXObject("Msxm12.XMLHTTP");
    } catch (othermicrosoft) {
      try {
        request = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (failed) {
        request = null;
      }
    }
  }
  if  (request==null)
    alert("Erro creating request object!");
  return request;
}