gistfile1.txt

var message_box = $('item42').setStyle('z-index: 1000');
$$('body').first().insert(message_box.remove());
var jar = new CookieJar({expires: ''});
//you can also set expires to any number of seconds
if(!jar.get('hide_message')){
  message_box.show().observe(
    'click',
    function(evt){
      jar.put('hide_message',true);
      this.hide();
    }
  );
};