<!DOCTYPE html>
<html>
<head>
<style>
input:valid {
background-color: yellow;
}
</style>
</head>
<body>
<h3>A demonstration of the :valid selector.</h3>
<input type="email" value="support@exampel.com">
<p>Try typing an illegal e-mail address, to see the styling disappear.</p>
<p><strong>Note</strong>: The :valid selector is not supported in Internet Explorer 9 and earlier versions.</p>
</body>
</html>