Get rid of the <tr> <td> <center> stuff - you don't need it, and it is currently invalid HTML due to missing elements.

You pulled the <div but then put in an extra </div>, so it is now unbalanced in the other direction.
PHP Code:
<?php
/**
 * blank sidebox - allows a blank sidebox to be added to your site
 *
 * @package templateSystem
 * @copyright 2007 Kuroi Web Design
 * @copyright Portions Copyright 2003-2007 Zen Cart Development Team
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: blank_sidebox.php 2007-05-26 kuroi $
 */

  // test if box should display
  
$show_social true;

  if (
$show_social == true) {
     
$title =  BOX_HEADING_SOCIAL;
     
$title_link false;
     require(
$template->get_template_dir($column_box_defaultDIR_WS_TEMPLATE$current_page_base,'common') . '/' $column_box_default);
  }
 
?>
  <div id="Facebook">
    <a href="http://www.facebook.com/pages/The-Esoteric-Emporium/145421388812693?sk=wall"><img src="images/fb.png" width="50" height="50" alt="Facebook" /></a>&nbsp;&nbsp;<a href="http://twitter.com/YOUR-TWITTER-HERE"><img src="images/tw.png" width="50" height="50" /></a>
  </div>