spelling-error.html

<!doctype html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, user-scalable=no">
  <title>::spelling-error擬似要素</title>
  <style>
  textarea {
    font-size: 18px;
    width: 300px;
    height: 100px;
  }

  ::spelling-error {
    color: red;
    background-color: pink;
  }
  </style>
</head>
<body>

<h2>textarea要素</h2>

<textarea>
  I'm a cat.
</textarea>
  
<textarea class="-invalid">
  I'm a cato.
</textarea>
  
<h2>p要素にcontenteditable属性</h2>
  
<p contenteditable>
  I'm a cat.
</p>
  
<p contenteditable class="-invalid">
  I'm a cato.
</p>

</body>
</html>