Ajax.Responders.register({
   onCreate: function() { new Effect.Appear('ajax-indicator', { duration: 0.3 }); },
   onComplete: function() {
     if (0 == Ajax.activeRequestCount)
       new Effect.Fade('ajax-indicator', { duration: 0.3 });
   }
});

function ajaxTour(url) {
    new Ajax.Request(url, {asynchronous:true,method: 'GET', evalScripts:true, on404:function(request){alert('Page not found');}});
}