An interesting question/issue has been posted over at WebmasterWorld:

On the 16th of May, I noticed that most of the websites that were in the first page rankings in Google USA, had been dropped to second and third page positions. Websites that have replaced them are mostly irrelevant listings from large corporate companies and over-bidded newbies. Is this a glitch in the system, as I don’t see how this would increase Googles’ revenue if they have a much lower click through rate or if surfers eventually block them out of their vision like they do with banners?

There are a few reasons why your ads’ placement will vary from query to query; and eventually disappear completely. First, keep in mind that the ad position that is listed within your AdWords campaign is an aggregate average. Your average ad position may be 3.2 but this means that your ad placement could be fluctuating between 1 and 5.2 and this discrepancy could surface from one search query to the next (an ad’s performance usually doesn’t oscillate this much, but in theory it could). However, if you’re average rank is around 3 but you are finding your ads dropping to the second page and disappearing, that could be an entirely different can of worms.

The number of search queries conducted by an individual will influence their paid search results; this is what you could be witnessing. Suppose you check your ad rank for your most trafficked keyword; upon your initial search query your ad should be listed in the approximate position of your average ad rank displayed within AdWords. However, if you search on that keyword a number of times you’ll notice that yours and your competitors’ ad rankings begin to shift. This fluctuation is not happening in the entire Google system, but solely within your browser.

If you are searching on the same term (or related terms) frequently, without clicking on any of the paid placements, Google will shift its ad serving algorithm, and your ad (and your competitors ads) will begin to display in varying ranks, soon dropping to the second page and eventually disappearing completely. Now, with the relevant ads being dropped due to repeated queries of the same keyword, ads with lower quality scores, which are usually have poor placement, may begin to creep up into the results.

Considering when you delete your browser cookies your ad results are set back to normal, then I think this is a measure by Google to combat impression fraud. I talked with my Google rep and she neither confirmed nor denied my suspicion – but I’m sticking to it!

Repeated search queries within a single browser will eventually alter the paid search results – but only in that specific browser.

In summary, your ad rank will naturally move around between queries, while maintaining an aggregate average of where you want your ad to appear. However, repeated search queries within a single browser will eventually alter the paid search results – but only in that specific browser. Question: I wonder how many times you need to search on a term in order for Google to begin altering your search results?