My problem is that the back button causes the browser to say something like "Page expired" when the previous page was created by a form.
Example:
Now when the visitor clicks the back button in the browser it will show something like "Page expired".
Instead the previous page should be shown with no warnings (page2, with the userlist)
How are your strategies to get around this behavior?
If you are submitting a form with search parameters, you are trying to get some data, not modify some.
So, you should use the HTTP GET method, and not POST : POST should be used when you intend to create/modify data, and GET should be used when you intend to fetch some data.
Or, if you have some create/modify operation that has to be done :
Location
HTTP header.See the Post/Redirect/Get page on wikipedia, about this.