document.observe('dom:loaded', function() {
  Event.observe($('tablebody'), 'mouseover', tableOverOut);
  Event.observe($('tablebody'), 'mouseout', tableOverOut);
});

function tableOverOut(event) {
  var el = event.element();

  var tr = $(el).up('tr');
  $(tr).childElements().each(function(element, index) {
   	$(element).toggleClassName('over');
  });
}