Make the text field display Credit Card when there's no value in it.

<html>
<head><style>body {min-height: 300px;} input { font-size: 16px; } textarea { font-size: 16px; } </style></head>
<body>
  <h3>Check Out</h3>
<input type="text" placeholder="Credit Card">
<input type="text" placeholder="Phone number">
</body>
</html>]]>

Make sure to pick placeholder.