I've cleared the cache in firefox 21.0, but the following excerpt does not display anything in firefox, but works as expected in ie.
(The script is to remind my wife to turn off the printer when she completes her session.)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
	<title>Special Event Recap lessons</title>
	<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=utf-8" />
	<meta name="description" content="Lesson Summary Worksheet" />
	<meta name="robots" content="noindex, nofollow" />
	<link rel="shortcut icon" href="..." />
	<link rel="stylesheet" type="text/css" href="..." media="screen" />
	    <link rel="stylesheet" type="text/css" href="..." media="screen" />
  <script language="javascript">
		function reminder() {
			alert("Please remember to shut off printer");
<body onunload="reminder()">