I have a website that is designed to be run at a kiosk at public events. I want users to be able to share a page from this site on Facebook without leaving their Facebook session logged in. This is not a Facebook Connect site (there's no login to synchronize w/FB), all I have is a link for sharing that goes to Facebook's sharer.php:

<a href="http://www.facebook.com/sharer.php?u="http://mysite.com/mypage">share this</a>

It allows the user to log in and posts the link fine, but then closes the window and leaves the user logged in. There is no option for logging out, so the next user that comes along and wants to share has the previous user's FB account logged in!

Seems like this just changed when Facebook's UI changed recently; previously it would redirect to the user's profile page after posting, from which they could log out.

How can I fix this? Any recommendations on the "right way" to allow sharing with FB from a public kiosk?