category 404 error

Hi, I’m having a problem with the 404 page generated on my category templates. The 404 page itself works fine, but I have the following code at the end of all my category-templates:

<?php else : ?>

<div class=”post”>
<h2>Not Found!</h2>
<p>Sorry, but you are looking for something that isn’t here.</p>
</div>

<?php endif; ?>

When the 404 is loaded, the post is loaded fine but the sidebar and footer have a smaller width than the rest of my site for some reason, not sure why. They also appear below the 404 post. You can see what I mean here: http://vivaskate.com/?cat=21

Thanks for any help,

Nick