Untitled

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
	<title></title>
  </head>
  <body>
	<div>
		<a><h1></h1><div>abc</div></a>
	</div>
	<script>
		//this line fails in FF
		document.getElementsByTagName('h1')[0].innerHTML = 'some H1';

		//show the result
		document.write(document.getElementsByTagName('div')[0].innerHTML.replace(/</g, '<').replace(/>/g, '>'));
	</script>
  </body>
</html>