It's a javascript script, it has to be include in a script tag
THE SCRIPT NODE MUST CONTAIN THE ID SPECIFIED IN THE SAMPLE BELOW
Click here to access to test page
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<body>
<script type="text/javascript" id="dyduchatbox" src="chatbox.js"></script>
<a href="#" onclick="togglePopin(true)">Display the chatbox</a>
</body>
</html>