The html code includes javascript to check if Java Runtime is installed in your browser.

example.html

<div id="my_output_div"></div>
<script src="http://java.com/js/deployJava.js"></script>
<script type="text/javascript">
    var html = '<ul>';
    html += '<li><b>Installed JREs:</b>' + deployJava.getJREs() + '</li>';
    html += '<li><b>Version Check (&gt;= 1.6.0?):</b>' + deployJava.versionCheck('1.6.0+') + '</li>';
    html += '<li><button onClick="deployJava.installLatestJRE();">Install latest JRE</button></li>';
    var div = document.getElementById('my_output_div');
    div.innerHTML=html;
</script>