window.addEvent('domready', function(){
  
  var original = $('menu').get('class');
  
  $$('#menu li a').addEvents({
    
    mouseenter: function(){      
      btnid = this.get('id');

      $('menu').setProperty('class', btnid);
		},

		mouseleave: function(){
      $('menu').removeProperty('class');
    }

  });
  
  $('menu').addEvents({
    mouseleave: function(){
      $('menu').setProperty('class', original);
    }
  });
  
});