var http = createRequestObject();

function createRequestObject() {
   var objAjax;
   var browser = navigator.appName;
   if(browser == "Microsoft Internet Explorer"){
      objAjax = new ActiveXObject("Microsoft.XMLHTTP");
   }else{
      objAjax = new XMLHttpRequest();
   }
   return objAjax;
}

function getTopMenu(){
   http.open('get','/menu/suckerfishmenu.html'); 
   http.onreadystatechange = updateNewContentTop; 
   http.send(null);
   return false;
}

function updateNewContentTop(){
   if(http.readyState == 4){ document.getElementById('topnav').innerHTML = http.responseText; }
}