Browser's back button

I’ve noted when the browser’s back button is pressed the view on browser go back but doubled (the original view with all datas and another view-same clear appended on bottom). On the contrary if I go back with navigator (… navigateTo(…)) all is ok.
Any ideas?
Thaks for all.

For a better explanation: two snapshot of screen: first before calling a menu function, second after coming back with backbutton.

My mistake: the correct use of Navigator is:
nav.addView(name_of_view, ClazzView.class);
nav.addView(name_of_view, new ClazzView());