Add JavaFX to Web Pages with Applets - JavaFX: Developing Rich Internet Applications - page 250

color: Color.rgb(100,100,100)
},
]
}
}
action: function() {
stage.close();
}
}

The second concept is that when the button is clicked, the action calls the stage's
close() function. The stage.close() function then causes the application to be
again docked to the browser page, if that page is still visible. Figure 9.6 shows the
application redocked. Notice the close button does not show when it is docked.

Figure 9.6 Docked Applet