Restriction issue with using URL redirection

I used S2member/WP to create a simple membership area (no paypal, just free submission level 0). Everything works just fine except: Instead of setting up the Log-In Welcome page in WP/S2Member I used the ‘Special Redirection URL’ at the bottom field in S2memeber, because all my pages are already done in HTML.

What it does is that it seems there is zero security at all. It feels like you are outside of a secured membership area, I can flip back and forward within the browser, eg after SIGNOUT I go back with the browser and here we are: last sign-in page easy to access. I also can see the URL in the browser. When I copy and paste that URL I have access directly to the membership area, without prompting me to the member log-in.

Anybody experienced the same? It looks like an easy fix or no fix when working with URL/HTML pages only (but why would that redirection section exist then??)

Please see test webpage http://www.baerig-design.com, sing-in with user:tester and password:test11

THANK YOU SO MUCH FOR YOUR HELP,
Bob