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<!DOCTYPE html> <html> <title>W3.CSS</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="4/w3.css"> <body> <div class="w3-container"> <h2>Accordions</h2> <p>An accordion with lists:</p> <button onclick="myFunction('Demo1')" class="w3-button w3-block w3-black w3-left-align"> Accordion 1</button> <div id="Demo1" class="w3-hide w3-border"> <ul class="w3-ul"> <li>Jill</li> <li>Eve</li> <li>Adam</li> </ul> </div> </div> <script> function myFunction(id) { var x = document.getElementById(id); if (x.className.indexOf("w3-show") == -1) { x.className += " w3-show"; } else { x.className = x.className.replace(" w3-show", ""); } } </script> </body> </html>