Step 1.
Admin CP Look & Feel Select Template skin_shoutbox_hooks hookGlobalShoutbox
Find:
<input type='button' id='shoutbox-myprefs-button' value='{$this->lang->words['my_prefs']}' class='input_submit alt' />
Add below:
<input type='button' id='shoutbox-rules-button' value='{$this->lang->words['board_rules']}' class='right input_submit alt' />
Step 2.
Find:
<script type='text/javascript'>
//<![CDATA[
{$d['js']}
//]]>
</script>
Add below:
<div id='shoutbox-rules' style='display: none; line-height: 1.5;'>
<h3>{$this->lang->words['board_rules']}</h3>
<div class='ipsBox'>
<div class='ipsBox_container ipsPad'>
<p>Your rules text</p>
</div>
</div>
</div>
<script type='text/javascript'>
$('shoutbox-rules-button').observe( 'click', function(e) {
_var = new ipb.Popup( 'booboo', { type: 'pane',
initial: $('shoutbox-rules').innerHTML,
hideAtStart: false} );
Event.stop(e);
return false;
});
</script>
Effect: