I run an online news portal, similar to say NYtimes or WashingtonPost that has a number of sections - like Sports, News, Business,etc.
We periodically run a fullpage popover ad on the website homepage. This is an advertisement that will appear when someone enters the main domain name. The user may either click and open the ad in a new window or the page will redirect to the domain name after a 2-3 second period.
The popover ads are located at ads.example.com and so when I look into the Analytics data for the homepage, I naturally see a lot of ads.example on the referral list.
Now, what's interesting is that this referral also shows up on a number of sub-section pages. That is, on days when the popover ads are run, it is common to see the ads.example.com referral on my example.com/business, example.com/sports/joe-pa.html,etc.
How can this be possible? Has anyone experienced similar "impossible" scenarios with analytics?
(For what it's worth, all the sections are under the example.com domain and not separate subdomains - except for the ads.example.com bit)