[thelist] works in IE5.0 but not in Opera/NN

Hi all -

on this page, I retrieve values for a list box (lstAllAuthors) from the
DBserver.
After the list box is created, I create navigation buttons, to allow for
different actions.

The function goAender works in IE, but does nothing in Opera and NN.
Does anybody know why?

TIA
 Regards
Matthias Ritzkowski

Here's the code
-------------------------------------------------------------
<input type="button" name=btnAendern value="Ändern" onclick="goAender()">
<script type="text/javascript">
<!--

function goAender()
{
var ind = lstAllAuthors.options.selectedIndex;
//check if selection was made
var idx = lstAllAuthors.options(ind).value;
var url = "db_aender_author.php?id="+idx;
location.href =url;
}
// -->
</script>