Older Entries not working

Hi on my blog page: aidaprints.com/?page_id=16

I have older entries at the bottom of the page: when you click on this the entries remain the same. I have looked in the index.php and found this:

<div class="navigation">
<div class="alignleft"><?php next_posts_link('? Older Entries') ?></div>
<div class="alignright"><?php previous_posts_link('Newer Entries ?') ?></div>
</div>
<?php else : ?>
<h2 class="center">Not Found</h2>
<p>Sorry, but there are currently no posts found here.</p>
<?php endif; ?>
</div>
</div>

Any ideas?????????
Cheers J

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