​x
 
<html>
<head>
<script type="text/javascript">
function disable()
  {
  document.getElementById("check1").disabled=true
  }
</script>
</head>
<body>
​
<form>
<input type="checkbox" id="check1" />
<input type="button" onclick="disable()" value="Disable Checkbox" />
</form>
​
</body>
</html>
​