flex-QQmail.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body, html{
            margin: 0;
            height: 100%;
        }
        div{
            display: flex;
            flex-flow: column;
            height: 100%;
        }
        header{
            height: 100px;
            background-color: red;
        }
        main{
            flex-grow: 1;
            display: flex;
        }
        aside{
            width: 150px;
            background-color: lightgreen;
        }
        section{
            flex-grow: 1;
            background-color: lightblue;
        }
    </style>
</head>
<body>
    <div>
        <header>header</header>
        <main>
            <aside>aside</aside>
            <aside>section</aside>
        </main>
    </div>
</body>
</html>