Hi post lightbox

<?php if (has_post_thumbnail()): ?>
<div class="post-thumbnail">
<a rel="lightbox" href="<?php thumb_url();?>">
                                                    <img src="<?php echo mcresize_image(thumb_url(), 639, 289, 't'); ?>" alt="" width="639" height="289" />
</a>
</div><!-- end of post-thumbnail -->
<?php endif ?>