It used to be that if you got an email notification of a post in a category that's only available to people with logins to the IUG web site, and you clicked the link but you weren't logged into the IUG web site in your browser, you would see a 404 "page not found" error (and you would probably think something was broken). Now you'll see something more useful, a page that says "please log in."
Some of the categories that are only available to people who are logged into the IUG web site are:
Polaris and Polaris SQL
Clearing House Repository
Technology Services Coordinator
Cuyahoga Falls Library