function getXmlHttpObject(){
     var req;
     if(window.XMLHttpRequest) {
         req = new XMLHttpRequest();
         if (req.overrideMimeType) {
            req.overrideMimeType('text/xml');
         }
      }
      else if (window.ActiveXObject) {
        try {
          req = new ActiveXObject("Msxml2.XMLHTTP");
        }catch (e) {
          try {
            req = new ActiveXObject("Microsoft.XMLHTTP");
          } catch (e) {}
        }
      }
      return req;
}