(function(){
	var firsts = document.getElementById('nav').getElementsByTagName('li');
	for(var i = 0; i < firsts.length; i++){
		firsts[i].onmouseover = function(){
			this.className = this.className.replace('off','on');
		};
		firsts[i].onmouseout = function(){
			this.className = this.className.replace('on','off');
		};
	}
})();