Код IT Загрузка примера кода…

HTML main.html 
<!DOCTYPE html>
<html lang="ru">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>DOM-пример</title>
  <style>
    *, *::before, *::after { box-sizing: border-box; }
    body {
      margin: 0;
      padding: 1.5rem;
      font-family: system-ui, sans-serif;
      line-height: 1.5;
      background: #f8fafc;
      color: #1e293b;
    }
  </style>
</head>
<body>
  <main id="app">
    <!-- разметка примера -->
  </main>
  <script>
    // ваш JavaScript
  </script>
</body>
</html>
<!DOCTYPE html>
<html lang="ru">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>DOM-пример</title>
  <style>
    *, *::before, *::after { box-sizing: border-box; }
    body {
      margin: 0;
      padding: 1.5rem;
      font-family: system-ui, sans-serif;
      line-height: 1.5;
      background: #f8fafc;
      color: #1e293b;
    }
  </style>
</head>
<body>
  <main id="app">
    <!-- разметка примера -->
  </main>
  <script>
    // ваш JavaScript
  </script>
</body>
</html>