When you save your applet from AppletViewer,
you'll have an exception like this:
------
Unknown object of type:Hello11
Exception occurred during event handling:
java.lang.IllegalArgumentException: Unknown argument
        at java.text.MessageFormat.format(MessageFormat.java)
        at java.text.MessageFormat.format(MessageFormat.java)
        at java.text.Format.format(Format.java)
        at sun.applet.AppletMessageHandler.getMessage(AppletMessageHandler.java:76)
        at sun.applet.AppletViewer.appletSave(AppletViewer.java:418)
        at sun.applet.AppletViewer.handleEvent(AppletViewer.java:631)
        at java.awt.Window.postEvent(Window.java)
        at java.awt.MenuComponent.postEvent(MenuComponent.java)
        at java.awt.MenuComponent.postEvent(MenuComponent.java)
        at java.awt.MenuComponent.postEvent(MenuComponent.java)
        at java.awt.MenuComponent.dispatchEventImpl(MenuComponent.java)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java)