login session

Hi list
I have a login, It looks work well. But it's strange that when I close
the web browser and login system next day morning, it access system
directly that don't goto the login page and show me is the login last
day, When I logout via controller's method and zhen login again, the
login page is list.
I know there is something need be configure about session. But can't
find it.

Thanks for your help