function trail($separator = ' - ') {
      $trail_string = '<div xmlns:v="http://rdf.data-vocabulary.org/#">';
      for ($i=0, $n=sizeof($this->_trail); $i<$n; $i++) {
        if (isset($this->_trail[$i]['link']) && tep_not_null($this->_trail[$i]['link'])) {
          $trail_string .= '<span typeof="v:Breadcrumb">
                              <a href="' . $this->_trail[$i]['link'] . '"
                              rel="v:url"
                              property="v:title"
                              class="headerNavigation">' . $this->_trail[$i]['title'] . '</a>';
        }

        if (($i+1) < $n) $trail_string .= $separator;
        $trail_string .= '</span>';
      }
      $trail_string .= '</div>';
      return $trail_string;
    }