menuHover = function(nav) {
    var sfEls = document.getElementById("main_nav").getElementsByTagName("li");
    for (var i=0; i<sfEls.length; i++) {
      sfEls[i].onmouseover=function() {
        this.className+="over";
      }
      sfEls[i].onmouseout=function() {
        this.className=this.className.replace(new RegExp("\\s?over\\b"), "");
      }
    }

    var listItem = document.getElementById(nav).getElementsByTagName('ul');
    for(var i=0;i<listItem.length;i++) {
      listItem[i].onmouseover=function() {
        var changeStyle = this.parentNode.getElementsByTagName('a');
        changeStyle[0].className+="active";
      }

      listItem[i].onmouseout=function() {
        var changeStyle = this.parentNode.getElementsByTagName('a');
        changeStyle[0].className=this.className.replace(new RegExp("\\s?active\\b"), "");
      }
    }
  }

  function addEvent( obj, type, fn ) {
    if ( obj.attachEvent ) {
      obj['e'+type+fn] = fn;
      obj[type+fn] = function(){obj['e'+type+fn]( window.event );}
      obj.attachEvent( 'on'+type, obj[type+fn] );
    } else
      obj.addEventListener( type, fn, false );
    }
  function removeEvent( obj, type, fn ) {
    if ( obj.detachEvent ) {
    obj.detachEvent( 'on'+type, obj[type+fn] );
    obj[type+fn] = null;
    } else
      obj.removeEventListener( type, fn, false );
    }

  addEvent(window, 'load', function () { menuHover('main_nav'); });