Google has announced that it is collecting and storing data collected from searches users carry out on any search engine, and using it to better target ads to them on AdSense enabled sites they visit over the next few hours.

Google was already using the referral URL (the link a user followed to arrive at a site) as a factor in determining which ads to display on an AdSense enabled page.

Whenever a user arrives at a website after clicking a link in the search results of a search engine, the keyword terms they used in the search query are always appended to the referral URL (you can see this in your server logs).

On destination sites displaying AdSense ads, Google extracts this search term and treats it as part of the content of the site.

Google give the following example:

“The referral URL passed to your site may look something like this: http://www.google.com/search?q=golf+shop+atlanta.

To deliver the most relevant ad … we could use the additional information from the query words to show an ad for a golf shop in Atlanta rather than for one in Chicago (depending on the other words in the page).”

Now Google has gone a step further.  This search information is being stored in the advertising cookie on the user’s browser, and used to target ads to them on other AdSense enabled sites they may visit subsequently over the next few hours.

Google say, “After a short period of time (a few hours) the query words are no longer used for the purposes of matching ads.”

Note that Google doesn’t say the data is deleted. Or even that it is no longer used. They only say, “no longer used for the purposes of matching ads” (emphasis mine).

And although Google go on to remind us that users can opt out of its advertising cookie at any time here, realistically, how many non-webmasters will be aware that this is happening? Or even know about the advertising cookie and that they can opt out?

It might prove to be good for users of AdSense though. I have certainly noticed a jump in clicks on my AdSense ads over the last 2 days, though it’s too soon to draw any conclusions. Check your stats and see if you have a spike.

But if clickthroughs do increase appreciably, knowing Google they’ll probably gradually reduce the webmaster’s share of the ad price still further until there’s no net gain …  all too easy to do when you keep the formula a secret.

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