hi... i'm still new to seam

i made simple crud application
everything works fine
except that when i logged out from insert form and then pushed back button in the browser and then execute the process(persist),
seam allowed it to persist the data to db
i thought session is destroyed when i invoked identity.logout

anyway i wrote the following code to pages.xml to overcome this problem

 <page view-id="*">
 <navigation>
 <rule if="${not identity.loggedIn}">
 <redirect view-id="/login.xhtml"/>
 </rule>
 </navigation>

 </page>