HTML 5 app code for stackoverflow(not working)

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
                      "http://www.w3.org/TR/html4/strict.dtd">
<html>
  <head>
    <title>Cordova Menu Button Example</title>

    <script type="text/javascript" charset="utf-8" src="cordova-1.7.0.js"></script>
    <script type="text/javascript" charset="utf-8">

    // Call onDeviceReady when Cordova is loaded.
    //
    // At this point, the document has loaded but cordova-1.7.0.js has not.
    // When Cordova is loaded and talking with the native device,
    // it will call the event `deviceready`.
    //
    function onLoad() {
        document.addEventListener("deviceready", onDeviceReady, false);
    }

    // Cordova is loaded and it is now safe to make calls Cordova methods
    //
    function onDeviceReady() {
        // Register the event listener
        document.addEventListener("menubutton", onMenuKeyDown, false);
		document.addEventListener("volumedownbutton", onVolumeDownKeyDown, false);
			document.write("<h>ondeviceready</h1>");
    }

    // Handle the menu button
    //
    function onMenuKeyDown() {
	document.write("<h1>Menu</h1>");
    }

	function onVolumeDownKeyDown() {
	document.write("<h1>volume</h1>");
    }


    </script>
  </head>
  <body onload="onLoad()">
  </body>
</html>