Why am I getting a white area?

I want add "Add This" below Whois online sidebox

<?php
/**
 * Side Box Template
 *
 * @package templateSystem
 * @copyright Copyright 2003-2005 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: tpl_whos_online.php 2982 2006-02-07 07:56:41Z birdbrain $
 */
  $content = '';
  $content .= '<div id="' . str_replace('_', '-', $box_id . 'Content') . '" class="sideBoxContent centeredContent">';
  for ($i=0; $i<sizeof($whos_online); $i++) {
    $content .= $whos_online[$i];
  }
  $content .= '</div>';
  $content .= '';


?>
<!-- AddThis Button BEGIN -->
<div class="addthis_toolbox addthis_default_style ">
<a class="addthis_button_preferred_1"></a>
<a class="addthis_button_preferred_2"></a>
<a class="addthis_button_preferred_3"></a>
<a class="addthis_button_preferred_4"></a>
<a class="addthis_button_compact"></a>
<a class="addthis_counter addthis_bubble_style"></a>
</div>
<script type="text/javascript" src="http://s7.addthis.com/js/300/addthis_widget.js#pubid=ra-4d9f0913d28c8e79"></script>
<!-- AddThis Button END -->

This code show me Above the box .

what i do wrong ?

Thanks

<!-- AddThis Button BEGIN -->
<div class="addthis_toolbox addthis_default_style ">
<a class="addthis_button_preferred_1"></a>
<a class="addthis_button_preferred_2"></a>
<a class="addthis_button_preferred_3"></a>
<a class="addthis_button_preferred_4"></a>
<a class="addthis_button_compact"></a>
<a class="addthis_counter addthis_bubble_style"></a>
<script type="text/javascript" src="http://s7.addthis.com/js/300/addthis_widget.js#pubid=ra-4d9f0913528c8e79"></script>
<!-- AddThis Button END -->
   <?php echo '<a href="' . zen_href_link(FILENAME_ASK_A_QUESTION, 'products_id='
   . $_GET['products_id']) . '">' .   zen_image_button(BUTTON_IMAGE_ASK_A_QUESTION, BUTTON_ASK_A_QUESTION_ALT) .
   '</a>'; ?>

</div>

 <!--bof Product description -->
<?php if ($products_description != '') { ?>
<div id="productDescription" class="productGeneral biggerText"><?php echo stripslashes($products_description); ?></div>
<?php } ?>
<!--eof Product description -->

Why i get this ?

because your productMainImage is longer than your productPrices and your addthis_toolbox addthis_default_style