index.html

<!DOCTYPE html>
<html>

<head id="head">
  <title>Example HTML Website</title>
</head>

<body>
  <header>
    <h1>My Website</h1>
  </header>
  <nav>
    <ul>
      <li><a href="#">Home</a></li>
      <li><a href="#">About</a></li>
      <li><a href="#">Contact</a></li>
    </ul>
  </nav>
  <main>
    <h2>Welcome to My Website</h2>
    <p>This is a simple website.</p>
    <button onclick="addCSS()" id="button">Toggle CSS</button>

  </main>
  <footer>
    <p>Copyright © App Brewery</p>
  </footer>
  <script>
    let counter = 0
    function addCSS() {
      counter++
      if (counter % 2 !== 0) {
        document.getElementById("head").innerHTML = '  <title>Example HTML Website</title> \n<link rel="stylesheet" href="./styles.css" />'
      } else {

        document.getElementById("head").innerHTML = '  <title>Example HTML Website</title> '

      }
    }
  </script>
</body>

</html>