menu = function(idElement){
  Event.observe($(idElement),"click",function(event){
    var elt = $(Event.element(event));
  
    if (elt && elt.descendantOf($(idElement)) && elt.nodeName=='LI'){
  
      Event.stop(event);
  
      var its=$$('.selected_item').findAll(function(e){
        return !elt.descendantOf(e) && !e.descendantOf(elt) && e!=elt
      });
  
      elt.addClassName("selected_item");
  
      its.each(function(e){e.select("ul").invoke('hide')});
  
      its.invoke("removeClassName","selected_item");
  
      var ul=elt.childElements().find(function(e){return e.nodeName=='UL';});
      if (ul) {
        ul.setStyle({"display":"block"});
      }
    }
  });
}