IFrames as menu. 2 iframes side by side.

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
    <script src="script.js"></script>
  </head>

   <body>

<div class="menu">
<iframe src="menu.html" name="iframe_a" frameborder="1" scrolling="no" width="100%" height="512" >
  <p>Your browser does not support iframes.</p>
</iframe>
</div>
<div class="box">
<iframe name="iframe_b" frameborder="1" scrolling="no" width="100%" height="512">
  <p>Your browser does not support iframes.</p>
</iframe>
</div>
</body>

</html>

// Code goes here

/* Styles go here */

.box{
    width:70%;
    float:left; 
}
.menu{
    width:30%;
    float:left; 
}

<html>
  <body>
    <div>
      <ul>
        <li><a href="http://www.w3schools.com" target="iframe_b">W3Schools.com</a></li>
        <li><a href="https://www.bing.com/" target="iframe_b">Search Tool</a></li>
      </ul>
    </div>
  </body>
</html>