After running a search for Keyword A, I run a new search for Keyword B. The two keywords have no relationship to each other. (ie fishcake recipe & Microsoft)
The SERP for Keyword B includes one ad that also appeared for Keyword A. There's no way the advertiser would be bidding on Keyword B, and even if it was a broad, you'd never see it in this search result.
Running further searches for Keyword B fail to show the ad again. It only happens immediately after searching for the other keyword.
Guess: Google is experimenting - by adding a single ad from your previous search into the current SERP. People tend to make multiple searches on a single theme, so this might be a way of measuring how closely related consecutive searches might be, my seeing how often this out-of-place ad is clicked on.
I think I'll call it OOP Ad (out-of-place ad).
I'd like to think that Google would not use our $$ for their experiments, so perhaps we aren't being charged for any clicks
If so, log out and try again!
It may be that too few ads were available for B, and Google is filling up the space with a known interest of yours.
I'm guessing, but I doubt Google would 'force out' a relevant ad for an irrelevant one, even as an experiment!
I first noticed it when looking at unrelated subjects but which included the word, "accessories". When I did a search for "phone accessories" after a search for "truck accessories", mixed in with the phone ads were truck accessory ads.
If consecutive searches have some type of item in common such as a word or category, you can understand it might work. But there are also some really weird results.
I just did a search for "truck tires" followed by "running shoes" and along with the shoe ads was one for starting a tire store. There was no shoe or run words in the ad or URL.
I found if I refreshed the page or cleared the cookies, I'd get the correct results. This held for both IE and Firefox.
So obviously you have to be careful when using broad search keywords in your Adwords account.
