That Really depends upon the sensitivity and nature of the site. If your site is a site that often times has users that may stay at a page for longer then 20 minutes before moving to another page then that method might be a major nuisance to your users. You should really analyze the sensitivity of the information they are accessing and whether you think they might want to keep a browser open to check on something later on down the line. And of course always emphasize a Logout button in plain site so that users are made aware that there is a logout option
Hope this helps. Posting is provided as is and posted at 3am in the morning
WHen a session ends... it is important to call FormsAuthentication.Signout() ?
