You'll want to find:
Code:
<?php
}
?>
<td valign="top">
<!-- bof breadcrumb -->
in the tpl_main_page.php
and add your custom <div>
Code:
<?php
}
?> <div id="yourCustomDiv">
<td valign="top">
<!-- bof breadcrumb -->
and you'll need to find the best place to end that div. In my case, I put the footer inside this custom div, and ended the div after the footer. In your case you may want the footer to display across the whole page, in which case you would need to have the div ending somewhere just before the right column begins.