var request = null;
function createRequest() {
  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 ("Error creating request object!"); 
}