While the applet is loading, it displays a white rectangle for a second. How can we get rid of him?
If you are targeting Java 6, you can try the new plugin options to display the loading screen. http://www.oracle.com/technetwork/java/javase/plugin2-142482.html#LOADING_SCREEN
Have you tried loading your applet off-screen?
Then you can use MAYSCRIPT + LiveConnect so that your applet signal is triggered and JavaScript moves the applet container back to the screen.