function initMenu() {
    /*Comportement au survol de chaque élément de 1er niveau*/
    var menuElements = $$('#full_menu li.level-1');
    menuElements.each(function(element){
        element.observe('mouseout',function(){
            lock = false;
        });
        element.observe('mouseover',function(){
            while( typeof(lock)=='undefined' ){
                setTimeout(function(){
                        var allLayers = $$('#full_menu li.level-1 .layer');
                        var layerElement = element.childElements();
                        allLayers.each(function(layer){
                            if(layer != layerElement.toArray().last()){
                                layer.hide();
                            }
                        })
                        layerElement.toArray().last().show();
                    }
                ,500);
                lock=true;
            }
        });
        setTimeout(function(){
            delete(lock),
            500
        })
    });
}
Event.observe(window, 'load', initMenu);