If you open styles/prosilver/template/viewtopic_body.html
you'll find this at the top.
<!-- IF S_FORUM_RULES -->
<div class="rules<!-- IF U_FORUM_RULES --> rules-link<!-- ENDIF -->">
<div class="inner">
<!-- IF U_FORUM_RULES -->
<a href="{U_FORUM_RULES}">{L_FORUM_RULES}</a>
<!-- ELSE -->
<strong>{L_FORUM_RULES}</strong><br />
{FORUM_RULES}
<!-- ENDIF -->
</div>
</div>
<!-- ENDIF -->