flex-wrap

by rootjang

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    #container {
      display: flex;
      width: 500px;
      height: 300px;
      margin: 0 auto;
      -ms-flex-wrap: wrap;
      -webkit-flex-wrap: wrap;
      flex-wrap: wrap;
      border: 2px solid black;
    }

    #container div {
      width: 200px;
      border: 2px solid black;
      background: #ccc;
    }

    h2 {
      font-size: 20px;
      font-weight: bold;
      padding: 20px;
    }
  </style>
</head>
<body>
  <div id="container">
    <div id="box1"><h2>1</h2></div>
    <div id="box2"><h2>2</h2></div>
    <div id="box3"><h2>3</h2></div>
  </div>
</body>
</html>