var xmlReq=getXMLReq();
function getXMLReq() {
     var http_request = false;
     if (window.XMLHttpRequest) { // Mozilla, Safari, …
         http_request = new XMLHttpRequest();
     }else if (window.ActiveXObject) { // IE
          try {
               http_request = new ActiveXObject("Msxml2.XMLHTTP");
          } catch (e) {
               try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
               } catch (e) {}
          }
     }
     return http_request;
}