Trying to put a line between post

Hello, Im trying to put a line between my post. Ive read a couple ways but cant seen to make it work.

Here is my main index php post section:

<div id=”contentleft”>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<h1>” rel=”bookmark”><?php the_title(); ?></h1>
<?php the_time(‘F jS, Y’); ?>
<p>Filed Under <?php the_category(‘, ‘) ?></p>

<?php the_content(__(‘Read more’));?><div style=”clear:both;”></div>

<!–
<?php trackback_rdf(); ?>
–>

<?php endwhile; else: ?>

<p><?php _e(‘Sorry, no posts matched your criteria.’); ?></p><?php endif; ?>

<h1>Comments</h1>
<?php comments_template(); // Get wp-comments.php template ?>
</div>
<hr />
</div>

can somebody tell me where I put the <hr /> to make a line show up after all post?

Also where is the can I put the custom style code for the hr anywhere in my css? I was going to put it at the bottom.

Id like the line to be like 2px light grey.

Thanks