applet context error

[brobbs]

i have the following error message when i do
win = JSObject.getWindow(this);
js = new URL("http://localhost:8080/learn/applet/MyTest .html"); getAppletContext().showDocument(js);

Exception occurred during event dispatching:
java.lang.NoClassDefFoundError: netscape/javascript/JSObject
at Vasxe.actionPerformed(Vasxe.java:266)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Unk
n Source)
at j

can any body help me with this error ?