Problem trying to restore last visited page

Was it described too complicated?

Is it maybe possible to automatically reload the website with the proper
content once it's loaded and it detected a session?

I couldn't find any way how to display the website with render :update
only (page.html or something).

Would it be possible to do a AJAX call onLoad for body? Can't really
find anything for that but I think I read something about it
somewhere...