<html>
<head>
<style>
input:checked
{
background:#ff0000;
}
</style>
</head>
<body>
<form action="">
<input type="radio" checked value="male" name="gender"> Male<br>
<input type="radio" value="female" name="gender"> Female<br>
<input type="checkbox" checked value="Bike"> I have a bike<br>
<input type="checkbox" value="Car"> I have a car
</form>
<p><b>Note:</b> This example works properly only in Opera!</p>
</body>
</html>