Can’t position credit line properly

Hello. I’m trying to tweak theme andreas01-12 to add a credit for an editor on the left sidebar. Here is the relevant bit of code with the mod in question on the last line before the close div tag:

<div id="leftside">

<?php if ( function_exists('dynamic_sidebar') && dynamic_sidebar('Main Sidebar') ) : else : ?>

<h2 class="hide">Main menu:</h2>
<ul class="page">
<?php if (is_page()) { $highlight = "page_item"; } else {$highlight = "page_item current_page_item"; } ?>
<li class="<?php echo $highlight; ?>"><a href="<?php bloginfo('url'); ?>">Home</a></li>
<?php wp_list_pages('sort_column=menu_order&depth=1&title_li='); ?>
</ul>
<?php endif; ?>
<span style="top-margin: 30px; border-top: solid #FFFFFF">Production Editor: Kris Acheson</span>
</div>

My intent is to put a line between the credit and the menu and to add some top space before the credit. No matter that I try (p tag instead of span, absolute position instead of margin, etc.) the credit stubbornly stays right below the menu with no border above. What am I doing wrong?

TIA…….Steve