<html>
<body>
<p>You should see two 'hello world' frames below, each in 'view source' mode.</p>
<hr>
<iframe viewsource src="data:text/html,<p>hello world</p>"></iframe>
<iframe src="data:text/html,<frameset><frame viewsource src='data:text/html,<p>hello world</p>'></frameset"></iframe>
</body>
</html>