How to pass div id and querystring through anchor tag link

[deepthi.21456]

When i click on link i have to show div.I am sending div id and query string value through anchor tag link.But,i am not getting the query string value.This is my code

<a href="#cart?product_name=<?php echo $row['product_name'];?>"></a>
<div id="cart">
<?php
echo $_GET['product_name'];
?>
</div>