The Google AdSense blog announced that they are now using a form of search history in the way they contextual match the ads you see on third-party web sites.
AdSense used query data in the referrer URL to better match those ads. So if you came from Google or Bing, to a third party web site, often the referrer data would show query data in the path. Google would use that data to better target the ads on the web site.
What is new here? Well, Google is now storing this query data for “few hours” in your Google cookie data. So if you searched for something and clicked through to a site with AdSense ads on them, Google would store that query that lead to that web site and use it 2 or so hours later, when you visited another web site with AdSense ads on them.
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