window.addEvent('domready', function() {
    Register_TopNav();
    $$('#nav-challenges a')[0].addEvent('click', function(e) { e.stop(); });
});
function Register_TopNav() {
    $$("#nav ul").getParent().addEvents({
        mouseover: function() {
            this.getElements('ul').each(function(el) { el.addClass('hoverUL'); });
            this.getElements('div').each(function(el) { el.addClass('hoverDIV'); });
        },
        mouseout: function() {
            this.getElements('ul').each(function(el) { el.removeClass('hoverUL'); });
            this.getElements('div').each(function(el) { el.removeClass('hoverDIV'); });
        }
    });
}