HTML Code

<!DOCTYPE html>
<html>
<head>
  <title>CSS :first-child vs :first-of-type</title>
  <style>
    body {
      font-family: system-ui, sans-serif;
      padding: 1.5rem;
    }

    .box {
      padding: 0.35rem 0.75rem;
      background: #f1f5f9;
      border-radius: 0.35rem;
      font-size: 0.8125rem;
      color: #64748b;
      margin-bottom: 0.5rem;
    }

    /* Does NOT match — div is first child */
    p:first-child {
      border-left: 4px solid #ef4444;
      padding-left: 0.75rem;
    }

    /* DOES match — first p among siblings */
    p:first-of-type {
      border-left: 4px solid #2563eb;
      padding-left: 0.75rem;
    }
  </style>
</head>
<body>
  <h1>Comparison</h1>
  <div class="box">&lt;div&gt; is the first child</div>
  <p>First paragraph — blue border from :first-of-type only.</p>
  <p>Second paragraph.</p>
</body>
</html>

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