At the moment we cannot give slideshows and photo overlays/lightboxes
unique ids, like div class="the-overlay" id="530834" because there is no
apparent way to get this ID number from the photo/slideshow ID numbers in
the database. We need it so that we can give the links to the overlays
matching attributes (like rel="530834") so that we can have multiple
slideshows on a single page and have each open the correct overlay/lightbox.
Original link: http://code.google.com/p/ipm-wordpress/issues/detail?id=13