Apply Protaculous to the page, choose scriptaculous-packed, paste this into the top Function Body dialog.

fading menus for CSS Menu Action.js

document.observe('mouseover',function(evt){
  var elm;
  if((elm = evt.findElement('li.fwNavItem')) && elm.down('ul.sub')){
    elm.select('ul.sub').invoke('hide').invoke('appear',{duration:0.3});
  }
});