Event.observe(window, 'load', function()
{
  $$('a').each(function(a){
    if(a.getAttribute('target') == '_blank')
    {
      Event.observe(a, 'click', function(e)
      {
        Event.stop(e);
        window.open(a.href, 'gallery', 'width=600,height=600');
      });
      a.onclick = function(){ return false; };
    }
  });
});