Full validation example with javascript:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Radio button: full validation example with javascript</title>
<script>
function send() {
var genders = document.getElementsByName("gender");
if (genders[0].checked == true) {
alert("Your gender is male");
} else if (genders[1].checked == true) {
alert("Your gender is female");
} else {
// no checked
var msg = '<span style="color:red;">You must select your gender!</span><br /><br />';
document.getElementById('msg').innerHTML = msg;
return false;
}
return true;
}
function reset_msg() {
document.getElementById('msg').innerHTML = '';
}
</script>
</head>
<body>
<form action="" method="POST">
<label>Gender:</label>
<br />
<input type="radio" name="gender" value="m" onclick="reset_msg();" />Male
<br />
<input type="radio" name="gender" value="f" onclick="reset_msg();" />Female
<br />
<div id="msg"></div>
<input type="submit" value="send>>" onclick="return send();" />
</form>
</body>
</html>
Regards,
Fernando