var req = createXMLHttpRequest();  
   
 function createXMLHttpRequest() {  
  var ua;  
  if(window.XMLHttpRequest) {  
  try {  
   ua = new XMLHttpRequest();  
  } catch(e) {  
   ua = false;  
  }  
  } else if(window.ActiveXObject) {  
   try {  
     ua = new ActiveXObject("Microsoft.XMLHTTP");  
   } catch(e) {  
     ua = false;  
   }  
  }  
 return ua;  
}