圣杯布局(grid版) -

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>圣杯布局(grid版)</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        body * {
            background-color: chartreuse;
        }
        body {
            display: grid;
            grid-template-columns: 200px minmax(400px, 1fr) 200px;
            grid-template-rows: 10em minmax(calc(100vh - 20em - 0.6em), 1fr) 10em;
            gap: 0.3em;
        }
        header,
        footer {
            grid-column: span 3;
        }
    </style>
    </head>
    <body>
        <header>页眉</header>
        <aside>左侧</aside>
        <main>主题</main>
        <aside>右侧</aside>
        <footer>页脚</footer>
    </body>
</html>