[SOLVED] Custom Category Page

Hi,
i would like to know why following problem happened.

I was developing my new sub-domain so i need to customi one category inserting a table and other things.
BUT
it happened that
the same table pubblished in a post is properly displayed: i.e. with border-collapse:collapse
( see the attachment)
but copied inside the category page, the table is not displayed properly:
category-6.php

Thanks