<html>
<form id="radiobuttons" name="radiobutton">
<input id="rad1" value="a" type="radio" name="check"/>male
<input id="rad2" value="b" type="radio" name="check"/>female
<input id="rad3" value="c" type="radio" name="check"/>other
</form>
<body>
<script>
radiobtn = document.getElementById("rad1");
radiobtn.checked = true;
</script>
</body>
</html>