Can't call javascript from mozilla XUL? Probably trival, beginner troubles..

[Nick Reyntjes]

Hi everybody,
I'm new to mozilla XUL and am trying to play around a bit, but having
some problem starting..

Can anywone please tell me what is wrong with this:

<?xml version="1.0"?>

<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>

<window id="example-window" title="Example 8.6.2"
xmlns:html="http://www.w3.org/1999/xhtml"
xmlns="http://www.mozilla.org/keymaster/gatekeeper/
there.is.only.xul">
<script type="application/x-javascript">
function myfunction() {
alert("HELLO");
}
</script>
<button label="test" onclick="myfunction()"/>
</window>

If the button is clicked it does not show hello in my firefox 3.0.6
(Mozilla/5.0).

Thx!