A popup message after session timeout
When the session timeout is set and a user leaves an unsaved form for a while so their session expires and clicks on the Save button, they is redirected to the login page and all unsaved data from the form just being edited are lost.
The same frustrating situation can happend when you write a long wiki page.
The flash message on the login page does't help to recover lost data.
I thing that the user should be warn before data are lost.