<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
<head>
<script>

function boom()
{
  var listbox = document.getElementById("listbox");
  var td = document.getElementById("td");

  var listitem = document.createElementNS(XUL_NS, "listitem");

  listbox.appendChild(listitem);
  listbox.appendChild(td);
}

var XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";

</script>
</head>

<body onload="boom();">

<table><tbody><tr><td id="td">X</td></tr></tbody></table>

<xul:listbox id="listbox"/>

</body>
</html>