Back Button

In my Ajax app, handling the back button is a separate task in itself, we never even used to think of it with the old static html.

The questions here are?

1. What are the states that are back navigable?

2. How do I ensure consistancy of the presented information even while providing backbutton support.

E.g.

Inbox (Mails listed)—> View mail (by clicking a listed mail) —> Inbox (by click on Inbox link) —> Delete the viewed mail (See alterd listing of mails).

Now I click the browser’s Back button. Should I see the previous listing before mail deletion?

and click the browser’s Back button again. Should I be seeing the deleted mail?

If Yes are we undoing the action of deletion? isint it inconsistant behavior?

If No arent we making the Back button inconsistant?