[jQuery] class toggle navigation

[jQuery] class toggle navigation

Hello
I'm trying to implement a minimal navigation bar using jQuery's
toggleClass() function but can't seem to get it working, no matter how
many tips from all you gurus out there that I follow meticulously.
It's the .img_selector div at the bottom of the page:
http://www.thomasrugani.com/static/designobjects/02.html
I want to toggle the 'active' class for each <a> when it's selected,
to indicate which image is showing, so after calling jQuery, in the
<head> I've got
    <script type="text/javascript">
     $(document).ready(function(){
$('a').click(function () {
$(this).toggleClass('active');
});
});
    </script>
then the links, which also include the showPic function:
---------------
<div class="img_selector">
Image &nbsp;
    <ul>
        <li><a class="active" onclick="return showPic(this)" href="images/
stoppino_tictacs_lit.jpg" title="">01</a></li>
        <li><a onclick="return showPic(this)" href="images/
stoppino_tictacs.jpg" title="">02</a></li>
        <li><a onclick="return showPic(this)" href="images/
stoppino_tictac_base1.jpg" title="">03</a></li>
        <li><a onclick="return showPic(this)" href="images/
stoppino_tictac_base2.jpg" title="">04</a></li>
    </ul>
</div>
--------------------
Can anyone see what I'm missing? Thanks in advance..
Bernard