<html>
<head>
<style>
input:focus
{
background-color:yellow;
}
</style>
</head>
<body>
<form action="demo-form.php" method="get">
First name: <input type="text" name="fname"><br>
Last name: <input type="text" name="lname"><br>
<input type="submit" value="Submit">
</form>
<p><b>Note:</b> IE8 supports the :focus pseudo-class only if a !DOCTYPE is specified.</p>
</body>
</html>