I created something similar. Check out http://www.helpmelearntheweb.com/sandbox/

Here's how I did it. Let's use HTML only as an example. If you can use jQuery, it's very easy:

<script>
$("#idtextarea").keyup( function() {
	 $("#idoutput").html($("#idtextarea").val());
} );
</script>
<textarea id="idtextarea"></textarea>
<div id="idoutput"></div>

The jQuery keyup function will trigger an update whenever something is typed into the textarea, and update the output div.

Good discussion. I also want something like this, but I wish that every form will be filled automatically based on the URL in the address bar (just like Google Translate). Can it be done only with JavaScript?

beeblebrox, is it possible for you post the full source code so we may try and implement it on our servers?

Thank you.