The new, all and featured listings are built by completely different template files, and have few if any of the same classes/ids to style. Your site/template appears to be built on a Zen Cart v1.3.7 base, and may not have a feature built into current v1.3.9 code
(* @version $Id: tpl_modules_products_new_listing.php 6096 2007-04-01 00:43:21Z ajeh $)
which puts a <hr> between each product in the listing. Your template has nothing unique enough to style a border between products in those listings. You would need to edit /includes/templates/your_template/tpl_modules_products_new_listing.php and its siblings to add the <hr>. The v1.3.9 file looks like this near the bottom:
PHP Code:
echo $display_products_description;
?>
</td>
</tr>
<?php } ?>
<tr>
<td colspan="3"><hr /></td>
</tr>
<?php
$products_new->MoveNext();
}
} else {