Intendevi qualcosa di simile ?

Codice per Chrome

codice HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function pluto() {
  var ban1 = document.implementation.createHTMLDocument('pippo');
  var ban2 = document.implementation.createHTMLDocument('caio');
 
  ban1.write('codice del primo banner');
  ban2.write('codice del secondo banner');
  document.getElementById('primoBanner').innerHTML   = ban1.body.innerHTML;
  document.getElementById('secondoBanner').innerHTML = ban2.body.innerHTML;
}
//-->
</script>
</head>
<body>
<div id="primoBanner"></div>
<hr/>
<div id="secondoBanner"></div>
<hr/>
<input type="button" value="Clicca" onclick="pluto()"/>
</body>
</html>