W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">
<body>

<img src="img_snowtops.jpg" alt="Snow" style="width:100%">
  <a class="w3-bar-item w3-button w3-red" href="#">Home</a>
  <a class="w3-bar-item w3-button" href="#">Projects <span class="w3-tag w3-red w3-right w3-margin-right">8</span></a>
  <a class="w3-bar-item w3-button" href="#">About</a>
  <a class="w3-bar-item w3-button" href="#">Contact</a>

<div class="w3-container w3-blue-grey w3-display-container">
    <span onclick="this.parentElement.style.display='none'" class="w3-button w3-blue-grey w3-display-topright">&times;</span>
    <p>Lorem ipsum box...</p>
  </div>
</div>

<div class="w3-container">
<h2>Sidebar</h2>
<p>Put any element inside the sidebar.</p>
</div>

</div>
      
</body>
</html>