Made customizable 404 page have a {STANDARD404} variable available to allow embedding the "default" 404 content.
<!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">
<head>
<title>Firebug</title>
<link rel="stylesheet" type="text/css" href="firebug.css">
</head>
<body>
<div id="toolbar" class="toolbar">
<a href="#" onclick="parent.console.clear()">Clear</a>
<span class="toolbarRight">
<a href="#" onclick="parent.console.close()">Close</a>
</span>
</div>
<div id="log"></div>
<input type="text" id="commandLine">
<script>parent.onFirebugReady(document);</script>
</body>
</html>