Firefox 25 and its probably due to a lack of javascript (sorry if this wastes your time) because what I see is this in Firebug:
<p>This setup should take less than 400 mb RAM on startup.</p>
<script>
...
</script>
<div style="margin-bottom:1em;padding:0;">
<noscript>
<code>
<pre style="overflow:auto;margin:0;padding:0;border:1px solid #DDD;"><!DOCTYPE html>...