Links not working in javascript

Greetings, i am using this function:

<script type="text/javascript">
$(function(){
$('li')
.css('pointer','default')
.css('list-style-image','none');
$('li:has(ul)')
.click(function(event){
if (this == event.target) {
$(this).css('list-style-image',
(!$(this).children().is(':hidden')) ? 'url(materiale/plus.gif)' : 'url(materiale/minus.gif)');
$(this).children().toggle('slow');}
return false;})
.css({cursor:'pointer', 'list-style-image':'url(materiale/plus.gif)'})
.children().hide();
$('li:not(:has(ul))').css({cursor:'default', 'list-style-image':'none'});});</script>

The problem is that my links are not opening anymore. Can anyone modify the function so that when clicking on an anchor it will corectly function and open in the parent page or in a new tab ? Thank you in advance.