asp.net masterpage

场景：asp.net MasterPage menu 选中 css 有关问题

asp.net MasterPage menu 选中 css 问题
母版页Manage.master,有如下导航

<div class="menu_box">

                    <h2 class="title">

                        <button class="menu_close">

                            -</button><span>装修设计案例</span></h2>

                    <ul id="menu">

                        <li><a href="AddCase.aspx" class="on">发布案例</a></li>

                        <li><a href="#">案例列表</a></li>

                    </ul>

                </div>

                <div class="menu_box">

                    <h2 class="title">

                        <button class="menu_close">

                            -</button><span>设计师管理</span></h2>

                    <ul>

                        <li><a href="#">添加设计师</a></li>

                        <li><a href="#">设计师列表</a></li>

                    </ul>

                </div>

                <div class="menu_box">

                    <h2 class="title">

                        <button class="menu_close">

                            -</button><span>建材管理</span></h2>

                    <ul>

                        <li><a href="BrandList.aspx">品牌列表</a></li>

                        <li><a href="Cat.aspx">商品分类</a></li>

                        <li><a href="AddProduct.aspx">添加商品</a></li>

                        <li><a href="ProductList.aspx">商品列表</a></li>

                    </ul>

                </div>

我想实现，当点击某个内容页时，显示选中状态。
效果图：如下

------解决方案--------------------
Refer this
http://www.cnblogs.com/insus/archive/2012/09/25/2700939.html