comments popup?

I put the comments tag in my page, the div that i have with the post and the comments is:

<div class="post">
<?php the_content(); ?>
<?php wp_link_pages(); ?>
<?php comments_popup_link(__('0 pretenders'), __('1 pretender'), __('% pretenders')); ?>
</div>

But when i click the link it just isnt a popup…
How to? plz help.