W3Schools Tryit Editor

<!doctype html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content=" initial-scale=1">
<body>
<div>
 <h2>W3.CSS Modal</h2>
 <p>Use w3-container classes to create different sections in the modal (e.g. header & footer).</p>
 <button>Open Modal</button>
 <div id="id01">
 <div>
 <header> 
 <span>&times;</span>
 <h2>Modal Header</h2>
 </header>
 <div>
 <p>Some text..</p>
 <p>Some text..</p>
 </div>
 <footer>
 <p>Modal Footer</p>
 </footer>
 </div>
 </div>
</div>
 
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://www.w3schools.com/w3css/tryit.asp?filename=tryw3css_modal2">(->オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://www.w3schools.com/w3css/tryit.asp?filename=tryw3css_modal2" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>		
</body>
</html>