From the forum owners homepage
the Graduate projects section:
Inhabited Web
I had this idea about a collaborative web application for many years. In short - the system embeds a small, simple visualization into web pages, next to the browser's scroll bar. Triangles are used to represent single users and their position on the current page (scroll position). Collectively, this allows you to see where people are congregating on a web page - perhaps next to a great deal, interesting news story, or funny video.
I believe this is something Chris runs from time to time to gather data for his studies.
http://slinging.org/forum/YaBB.pl?num=1257109223/1#1I'm guessing some action we perform prompts his application to ask for a login.