As far as I remember some browsrs have problems implementing body.innerHTML, something about the paths.
You can do something uber simple like this very easily
<html><head><title>Darksat Box</title>
<SCRIPT LANGUAGE="javascript">
function go() {
if (light.style.visibility == "visible")
{
light.style.visibility = "hidden";
}
else
{
light.style.visibility = "visible";
}
}
</SCRIPT>
</head>
<body>
<INPUT TYPE="button" VALUE="show/hide" onClick="go();">
<SPAN ID="light" Style="Visibility:visible;">
<h1>Content</h1>
</SPAN>
</body>
</html>
Or check out another solution here.
http://www.emanueleferonato.com/downloads/lightbox.html
