That happens a lot with me. I'll be reading a multi-page article at a site, get to the bottom of the page, click the button or link to go to the next page, and only then, since I'm not busy reading the page content anymore, notice the ad.

Just as I'm realizing that it is something I'm quite interested in and want to click it for more information, the next page loads and I've lost the ad.

It's quite annoying.