footer.phpに以下の記述を入れる．

</div><!-- #main -->
<footer id="colophon" role="contentinfo">
<?php

/*
* A sidebar in the footer? Yep. You can customize
* your footer with three columns of widgets.
*/

if ( ! is_404() )
get_sidebar( 'footer' );
?>

<div id="site-generator">
Copyright &copy; 1990-<?php echo date( 'Y' ); ?>
<?php bloginfo( 'name' );?>  ALL Rights Reserved.
</div>
</footer><!-- #colophon -->
</div><!-- #page -->
<?php wp_footer(); ?>