CSS not work in Javafx WebStart mode

my problem is when i compile and run the code in Standalone mode it use the .css getStylesheets in my Scene , but when i run it in the WebStart nothing is applyed just the standard look of JavaFx .

even if i use :

scene.getStylesheets().add(getClass().getClassLoader().getResource("/e1/login.css").toExternalForm());

the error given by the java console in the web browser is :

java.lang.NullPointerException
    at e1.E1.start(E1.java:68)
    at com.sun.javafx.applet.FXApplet2$2.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(Unknown

and the same code is working in the Standalone mode

please helpppppppp me !!!!!!