Each post in its own "box" ?

Ok so what ive like to do is have it so each post has a 15px bottom margin with a dashed line to show the start of each new post ?

this is what i have atm….

<!--LOOP START-->
    <div id="content-wrapper">
    <div id="content">
      <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
      <div id="post-wrapper">
        <div id="post-img">
          <?php
if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
  the_post_thumbnail();
}
?>
        </div>
        <div class="clear" id="post-title">
<a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">
            <?php the_title(); ?>
          </a>
        </div>
<div id="post-auth">
        <small>
        <?php the_time('F jS, Y') ?>
        by
        <?php the_author_posts_link() ?>
        </small></div>
        <?php the_content('Read on'); ?>
        <?php endwhile; else: ?>
        <p>
          <?php _e('Sorry Nothing found, please search again.'); ?>
        </p>
        <?php endif; ?>
      </div>
    </div>

     <!--LOOP END-->

and the style

#content-wrapper {
	width:710px;
	font-family: "Open Sans", sans-serif;
	font-size:13px;
	color:#333333;
	overflow:auto;
}
#content {
	width:450px;
	float:left;
	margin-right:20px;
	border-bottom-width: 1px;
	border-bottom-style: dashed;
	border-bottom-color: #333;

}
#post-wrapper {
	max-width:450px;
}
#post-img {
	width:450px;
}
img.wp-post-image {
        padding:9px;
	outline: 1px solid #111;
	border-top: 1px solid #555;
	padding: 10px;
	background: #333;
	margin-bottom:15px;
        margin-left:1px;
        margin-top:1px; }
#post-auth {
	font-size: 12px;
	color: #333;
	font-family: "Open Sans", sans-serif;
}
#post-title {
	font-size: 15px;
	color: #333;
	font-family: "Open Sans", sans-serif;
	text-transform:uppercase;
	font-weight:bold;
}

and i get this http://www.masterrenny.com << as u can see at the bottom it has the dashed line but not inbetween each post? how can i get it to do this? D:

thanks,
renny