var message = '画像の保存はご遠慮下さい';
    var ie = document.all;
    var n4 = document.layers;
    var n6 = document.getElementByld && !ie;
    function myHandler(ev)
     {
       if (ie && (event.button==2))
         {alert(message);return false;}
       if ((n6) && ev.button==2)
         {alert(message);}
     }
    if(n4) document.captureEvents(Event.MOUSEDOWN);
    document.onmousedown = myHandler;
    document.onmouseup   = myHandler;