So now we have a "Welcome Ad", and basically I could live with that. But when I start a day's CodeGuru activity by clicking the link in a thread update notification mail that should take me to the first new post in that thread, instead I get to the page with the ad, and when I then click "Skip this ad" at the upper right, I'm getting dropped at the forum root page, not the respective thread. But most annoying: At this point the thread that the link in the mail should initially have taken me to will be marked "read" and I need to find my way to the first unread post myself.
The ad apparently is only shown "the next day", where "next day" seems not to be determined by lifetime of the IE session or crossing midnight local time; perhaps it's the Windows session that counts or simply a certain timespan of inactivity. But that may actually not be relevant for the issue at all.