// function to create an XMLHttpClient in a cross-browser manner
 function initXMLHttpClient() {
     var xmlhttp;
     try {
         // Mozilla / Safari / IE7
         xmlhttp = new XMLHttpRequest();
     } catch (e) {
          // IE
          var XMLHTTP_IDS = new Array('MSXML2.XMLHTTP.5.0',
                                     'MSXML2.XMLHTTP.4.0',
                                     'MSXML2.XMLHTTP.3.0',
                                     'MSXML2.XMLHTTP',
                                     'Microsoft.XMLHTTP' );
          var success = false;
          for (var i=0;i < XMLHTTP_IDS.length && !success; i++) {
              try {
                   xmlhttp = new ActiveXObject(XMLHTTP_IDS[i]);
                      success = true;
                } catch (e) {}
          }
          if (!success) {
              throw new Error('Unable to create XMLHttpRequest.');
          }
     }
     return xmlhttp;
 }