anand84 - 4:13 am on Nov 29, 2011 (gmt 0)
Thanks a lot gerronmulder. It all seems to fit in now. I just checked and see that the 'direct' visits have all troughed a bit on those particular days, which explains a bit.
However, one unsolved issue is that while these ads.example.com referrals show a massive peak during the days we run those popover ads, there seems to be a few hundred referrals from these pages even on other days. While we may attribute this to cache normally, in this particular instance, where the referrals show up more due to sessions rather than cache, I am not clear how this referral would continue to show up even after we have stopped displaying the full-page popover.