function runNav() {
  var seriesNav = $('seriesNav');
  Event.observe(seriesNav, 'mouseover', function() {
    seriesNav.addClassName('activeRunNav');
  });
  
  Event.observe(seriesNav, 'mouseout', function() {
    if (seriesNav.hasClassName('activeRunNav')) {
      seriesNav.removeClassName('activeRunNav');
    }
  });
}

Event.observe(window, 'load', function() {

  runNav();

});