Disable button on Load

<input type = "button" name = "but1" id = "but1" value = "Click Me" disabled = false>
 
<script type = "text/javascript">
 
var tim;  // global variable
function disableCancel() {
tim = setTimeout(disableContinue, 2000);  // 2 seconds delay
} 
 
function disableContinue() {
document.getElementById("but1").disabled = true;
window.clearTimeout(tim);
}
 
disableCancel();
 
// Multiple onload function created by: Simon Willison
// http://simonwillison.net/2004/May/26/addLoadEvent/
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
	window.onload = func;
  } else {
	window.onload = function() {
	  if (oldonload) {
		oldonload();
	  }
	  func();
	}
  }
}
 
addLoadEvent(function() {
  disableField();
});	
 
</script>