Post a link to the site with the problem so that others may see it and offer informed suggestions on how it might be repaired.
to begin with, delete that code from your style.css:
<?php if (function_exists('get_recent_comments')) { ?>
<li><h2><?php _e('Recent Comments:'); ?></h2>
<ul><?php get_recent_comments(); ?></ul>
</li>
<?php } ?>
<?php if (function_exists('get_recent_trackbacks')) { ?>
<li><h2><?php _e('Recent Trackbacks:'); ?></h2>
<ul><?php get_recent_trackbacks(); ?></ul>
</li>
<?php } ?>
and then come back … 😉
