Blokada menu kontekstowego JS

<script language="JavaScript">

 <!--

var message="Sorry, we don't allow that on this site!."; // Put your message for the alert box between the quotes.

function click(e) {
if (document.all) {
if (event.button == 2) {
alert(message);
return false;
}
}
if (document.layers) {
if (e.which == 3) {
alert(message);
return false;
}
}
}
if (document.layers) {
document.captureEvents(Event.MOUSEDOWN);
}
document.onmousedown=click;
// -->

</script>