Make <#DLL> tag more restrictive so won't output querystring parameters if the action was the exit/logoff action (action=99).
UOttawa uses a language toggle JS button we put on their pages. If a user logs out and logs back in, the 99 form number is retained in the URL. If the user then goes to change the language, the JS will reload the page, within a separate web folder that houses the alternate language pages. Since the URL still has the 99 action, the user is logged off.
Kerry Keegan shared this idea