function Menu() {
    var navItems = document.getElementsByTagName("li");
    
    for (var i=0; i<navItems.length; i++) {
        if (navItems[i].className == "level1" ||
            navItems[i].className == "current") {
            navItems[i].onclick=function() {
               for (var i=0; i<navItems.length; i++) {
                   if (navItems[i].className == "current") {
                        navItems[i].className = "level1" 
                    }
                }
                this.className = "current";
            }
        }
    }
}