function initMenuElement(element) {
    element.addEvent('mouseenter', onMouseEnterMenuElement.bindWithEvent(element));
    element.addEvent('mouseleave', onMouseLeaveMenuElement.bindWithEvent(element));
}

function onMouseEnterMenuElement(event) {
    event = new Event(event);
    var link = $E('a', this);
    var subMenu = $(link.id + '_');
    if (subMenu) {
        subMenu.setStyle('visibility', 'visible');
    }
    link.addClass('actif');
}

function onMouseLeaveMenuElement(event) {
    event = new Event(event);
    var link = $E('a', this);
    var subMenu = $(link.id + '_');
    if (subMenu) {
        subMenu.setStyle('visibility', 'hidden');
    }
    link.removeClass('actif');
}

window.addEvent('domready', function() {
    $ES('li','menu').each(initMenuElement);
});