JavaScript – ウェブサイトの右クリックボタンを無効にする方法

<script>
    <!--
   //edit this message to say what you want
    var message = "Function Disabled";

    function clickIE() {
        if (document.all) {
            alert(message);
            return false;
        }
    }
    function clickNS(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 = clickNS;
    }
    else {
        document.onmouseup = clickNS;
        document.oncontextmenu = clickIE;
    }

    document.oncontextmenu = new Function("return false")
   //-->
</script>