当div设置 position: fixed;之后，如何将嵌套的div垂直居中

悬赏园豆：10 [已解决问题] 解决于 2015-12-22 09:24

我想让嵌套其中的两个DIV在一行中居中

<body>

<div id="top_nav">
    <div id="logo">
        <img src="images/logo.png">
    </div>
    <div id="nav">
        <a href="#">关于我们</a>&nbsp;&nbsp;/&nbsp;&nbsp;
        <a href="#">技术能力</a>&nbsp;&nbsp;/&nbsp;&nbsp;
        <a href="#">核心产品</a>&nbsp;&nbsp;/&nbsp;&nbsp;
        <a href="#">销售业绩</a>&nbsp;&nbsp;/&nbsp;&nbsp;
        <a href="#">网上订单</a>&nbsp;&nbsp;/&nbsp;&nbsp;
        <a href="#">联系我们</a>
    </div>
</div>

<div class="content">


</div>
</body>

body, div, a, img {
    font-family: "Arial";
    margin: 0;
    padding: 0;
}

#top_nav {
    background-color: #00B4CC;
    width: 100%;
    height: 85px;
    white-space: nowrap;
    position: fixed;
}

#logo {
    display: inline;
}

#nav {
    color: white;
    font-size: 18px;
    line-height: 130px;
    display: inline;
    white-space: nowrap;
    border: 1px solid red;
}

#nav a {
    color: white;
    text-decoration: none;
}

.content {
    border: 1px solid red;
    height: 1000px;
}