I did it in a better way. I used an iframe, gave it a name which the (nested iframe page) form page gets the value from the iframe tag. This is the best of all worlds because now my clients can simple enter an iframe anywhere on the landing page and pass the value of the iframe name to the aweber account.

The iframe tag
<div align="center"><iframe src="form1.php" name="trackingname" width="600" height="560" frameborder="0" scrolling="no"></iframe></div>

The form1.php file
<script language="JavaScript" type="text/javascript">
//alert(window.name);
//document.write(window.name);
var t = (window.name);
document.writeln('<INPUT TYPE="hidden" name="custom t" value="', t, '">');
//.......
</script>

Nothing is needed on the main parent page. I changed the code a long time ago to allow iframes on my pages - no problems.