navHover = function() {
   var lis = document.getElementById("nav").getElementsByTagName("li");
      for (var i=0; i<lis.length; i++) {
         lis[i].onmouseover=function() {
            this.className+=" over";
         }
         lis[i].onmouseout=function() {
            this.className=this.className.replace(new RegExp(" over"), "");
         }
      }
   }
window.onload = navHover;
document.getElementById('nav').getElementsByTagName('li')[0].className += ' first';