Alternatively, you could just return false from the click event:
$('div.toggle').hide();
$('ul.product-info li a').click(function(event){
$(this).next('div').slideToggle(200);
+ return false;
});
Which would stop the A-Href being triggered.
Note however, for usability reasons, in an ideal world that href should still go somewhere, for the people whom want to open link in new tab ;)