<if condition="is_member_of($bbuserinfo, x, x )"> x olanlar görmesini istediğin üye guruplarıdır.

Bu şekilde:

<if condition="is_member_of($bbuserinfo, x, x )">
<vb:if condition="(THIS_SCRIPT == showthread) AND ($post[postcount] == '1')">
  <div class="attachments">
        <div style="width: 100%; text-align: center">
       <center><iframe src="http://ad.hepsiburada.com/advEngine.aspx?accountID=xxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxxxx-xxxxxxxx&categoryID=17&sizeID=9" width="728px" height="90px" frameborder="0"  scrolling="no"></iframe></center>
      </div>
</div>
</vb:if>  </if>