XMLHttpRequestをとりあえず使う

<?xml version="1.0"?>

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

<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <script>

function hello(){

    var req = new XMLHttpRequest();

    req.open("GET", "file:///C:/lan.log/", false);

    req.send(null);

    alert(req.responseText);

}

  </script>

  <hbox>

    <button label="run" onclick="hello()" />

  </hbox>

</window>