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Test Info:

<!DOCTYPE html>
<html>
<head>
<title>CSS level4 Selector :required and :optional</title>
<link rel="author" title="LEE YUN HEE" href="mailto:zzirasi@gmail.com">
<meta name="assert" content="You should see a green input box.">
<link rel="match" href="selector-required-ref.html">
<style>
input {border:3px solid red;}
:required {border-color:green;}
:optional {border-color:green;}
</style>
</head>
<body>
<p>
You should see a green input box.
</p>
<p>
<input required>
</p>
<p>
<input optional>
</p>
</body>
</html>