仿淘宝点击小图出现大图效果

<div class="bigger">
                                <img src="images/bigger.png" alt="" id="pro_img" class="bigger" />
                                <script type="text/javascript" language="javascript">
                                    function change_img(source){
                                        document.getElementById("pro_img").src=source;
                                        }
                                </script>
</div>
//小图部分开始
<ul>
                                <li>
      　　　　　　　　　　　　　　　　　　<a href="javascript:change_img(‘images/bigger.png‘)"><img class="img_selected" src="images/pz_03.png" /></a>
                                </li>
                                <li><a href="javascript:change_img(‘images/pz_03.png‘)"><img src="images/pz_03.png" /></a></li>
                                <li><a href="javascript:change_img(‘images/bigger.png‘)"><img src="images/pz_03.png" /></a></li>
                                <li><a href="javascript:change_img(‘images/pz_03.png‘)"><img src="images/pz_03.png" /></a></li>
                                <li><a href="javascript:change_img(‘images/pz_03.png‘)"><img src="images/pz_03.png"/></a></li>
                                <li><a href="javascript:change_img(‘images/bigger.png‘)"><img src="images/pz_03.png" /></a></li>
                                <li><a href="javascript:change_img(‘images/pz_03.png‘)"><img src="images/pz_03.png" /></a></li>
                                <li><a href="javascript:change_img(‘images/bigger.png‘)"><img src="images/pz_03.png" /></a></li>

                                <div class="clear"></div>
 </ul>