css圣杯等高布局

三列布局
左右固定,中间自适应
中间内容优先加载
左右和中间等高(伪等高)

*三列都需要浮动
*使用margin-left为负设定边界(元素位置不改变)
*左右使用定位,使中间的内容显示
*使用padding-bottom和margin-bottom设置伪等高

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>圣杯布局</title>
    <style>
        .header{
            background-color: #1be497;
            color: #fff;
            height: 50px;
            border: 1px solid black;
        }
        .footer {
            background-color: #1be497;
            color: #fff;
            height: 50px;
            border: 1px solid black;
        }
        .left,.right {
            /* float: left; */
            background-color: #fb7400;
            color: #fff;
        }
        .middle {
            float: left;
            width: 100%;
            background-color: #f7b400;
        }
        .left {
            position: relative;
            left: -200px;
            width: 200px;
            float: left;
            margin-left: -100%;
            padding-bottom: 10000px;
            margin-bottom: -10000px;
       
        }
        .right {
            width: 200px;
            float: left;
            margin-left: -200px;
            position: relative;
            right: -200px;
            /* 等高布局 */
            padding-bottom: 10000px;
            margin-bottom: -10000px;
        }
        .clearfix::after {
            content: '';
            display: block;
            clear: both;
        }
        .container {
            padding: 0 200px;
            overflow: hidden;
        }
    </style>
</head>
<body>
    <div class="header">header</div>
    <div class="container clearfix">
        <div class="middle">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ab laboriosam iste tempore minima aliquam voluptatem, recusandae illum quidem, optio vero sunt, enim et labore saepe dignissimos explicabo harum porro. Nesciunt.</div>
        <div class="left">left</div>
        <div class="right">right</div>
    </div>
    <div class="footer">footer</div>
</body>
</html>