Untitled

<!doctype html>
<html lang="en">
<head>
  <style>
    html,
    body {
      height: 100%;
    }

    body {
      display: flex;
      flex-direction: column;
    }

    .content {
      flex: 1 0 auto;

      padding: 1rem;
      background: #e6f2ff;
    }

    footer {
      flex: 0 0 auto;

      padding: 1rem;
      background: #e6ffe6;
    }

  </style>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
  <title>Hello, world!</title>
</head>
<body>
<div class="content">content</div>
<footer>footer</footer>
</body>
</html>