View file sys/tpl/captcha.block.tpl

<img src="{$path}captcha.php?{$rand}" id="captcha" alt="..."/><br />
<script>function captcha_reload(){document.getElementById('captcha').src = "{$path}captcha.php?" + Math.random();}</script>
<a href="#" onClick="javascript:captcha_reload();">обновить</a><br />
<input type="text" name="captcha" size="4" maxlength="4"/><br />