​x
 
<html>
<head>
<script type="text/javascript">
function disable()
  {
  document.getElementById("gnome").disabled=true
  }
</script>
</head>
<body>
​
<form>
Human: <input id="human" type="radio" name="creature" value="Human" />
<br />
Animal: <input id="animal" type="radio" name="creature" value="Animal" />
<br />
Gnome: <input id="gnome" type="radio" name="creature" value="Gnome" />
<br /><br />
<input type="button" onclick="disable()" value="Disable choice" />
</form>
​
</body>
</html>
​