In mine, it is here
<form name="MarkRead" action="active.asp" method="post">
<input type="hidden" name="AllRead" value="Y">
<td align="center" bgcolor="<% =strHeadCellColor %>" valign="center" width="20">
<%If not(rs.EOF or rs.BOF) and (mLev > 0) then %>
<input type="image" src="<%=strImageURL %>icon_topic_all_read.gif" value="Mark all read" id=submit1 name=submit1 alt="Mark all topics as read" height="15" width="15" border="0" hspace="0" onclick>
<% else %>
<% end if %>
</td>
</form>