var Hover = new Class({
   initialize: function(selector) {
       $$(selector).each(function(element) {
           element.addEvent("mouseover", function() { this.addClass("hover"); })
           element.addEvent("mouseout", function() { this.removeClass("hover"); })
       });
   } 
});

window.addEvent("domready", function() {
    new Hover("div #navigation ul li");
    new Hover("div #subnavigation ul li");
});