I use Mark site read and Unread Content on a regular basis. Sometimes setting the site cookie with Mark site read doesn't seem to clear and on my next visit Unread Content some things that have not had new comments for days or weeks (sometimes months) show up as unread. As if the server only had partial access to the history when I hit Mark site read. It is obvious when I thought I hit Mark site read but didn't, and content from those days or week that I didn't read shows up again. Not a problem, but a curiosity. Maybe a limit to how big the cookie can be?