Dynamic Link in CMPS Navbar not working

[fotoplatz]

In my navbar I add following code:

<script language="Javascript" type="text/javascript">
<!--
function realchatPopup(url, nn, pu, au, hmac) {
var r = screen.height / screen.width;
var w = screen.width>800?1000:800;
var h = Math.round(w*r);
var c = function(s) { return encodeURIComponent(s).replace('!', '%21'); }
var rcw = window.open(url + '&nn=' + c(nn) + '&pu=' + c(pu) +'&au=' + c(au) + '&hmac=' + hmac + '&cu=cw', 'rc',
'width='+w+',height='+h+',status=no,toolbar=no,menubar=no,location=no,scrollbars =yes,resizable=yes');
rcw.focus();
}
//-->
</script>
<td class="vbmenu_control"><a href="$chatLink">Chat</a></td>

On the forum's navbar at forum.php it works fine, but at my index.php there is only a link to my domain....

Have anyone an idea?
Thanks
Tom