var request = null;
  function createRequest() {
    try {
      request = new XMLHttpRequest();
    } catch (trymicrosoft) {
      try {
        request = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (othermicrosoft) {
        try {
          request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (failed) {
          request = null;
        }
      }
    }
    if (request == null) {
      alert("Error creating request object");
    }
  }