CSS如何匹配到多个class的示例代码

<li id="menu_268098" title="账户信息查询" class="open">
        <li id="menu_270008" class="nav_sec" title="账户余额查询">
            <a href="#/p/payment.search.account_balance" class="dropdown-toggle">
                <span class="nav-title">账户余额查询</span>
            </a>
        </li>
    </ul>
</li>

<li id="menu_268098" title="账户信息查询" class="open active">
        <li id="menu_270008" class="nav_sec" title="账户余额查询">
            <a href="#/p/payment.search.account_balance" class="dropdown-toggle">
                <span class="nav-title">账户余额查询</span>
            </a>
        </li>
    </ul>
</li>

li.open.active{
  background-color: #fff;
}