<script type="text/javascript">  
  function openchat(){new _uWnd('chat','Tag Board',300,100,{align:0,shadow:0,close:1,autosize:1,maxh:500,minh:100,resize:0}, $("#chat").html() )}  
  </script>  
  <div style="display:none;" id="chat">$CHAT_BOX$</div>

<a href="#" onclick="openchat();">Open the Chat-Box</a>