function stripe(table)
{
  table.getElements('tr').each(function(tr,i) 
  {
    if(tr.getFirst().get('tag') != 'th') 
    {

      if(i%2!=0) tr.setStyle('background', '#DDEEFF');
    }
  })
}

window.addEvent('domready', function() { 
  $$('table').each(function(table){this.stripe(table);}, this);
});