How to disable right click on web page using JavaScript ?

<script language=javascript>
<!--
//Disable right mouse click Script
var message="Function Disabled!";
///////////////////////////////////
function clickIE4(){
if (event.button==2){
alert(message);
return false;}}
function clickNS4(e){
if (document.layers||document.getElementById&&!document.all){
if (e.which==2||e.which==3){
alert(message);
return false;}}}
if (document.layers){
document.captureEvents(Event.MOUSEDOWN);
document.onmousedown=clickNS4;}
else if (document.all&&!document.getElementById){
document.onmousedown=clickIE4;
}document.oncontextmenu=new Function("alert(message);return false")
// -->
</script>