Google Analytics was used by over 71 per cent of the domains, Google AdSense by over 35 per cent, and Google DoubleClick by over 26 per cent.

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The study was conducted in March of this year. And preliminary numbers from April indicate that Google trackers appeared on roughly 80 per cent of 766,000 distinct domains on the net. The researchers call Google "the most dominant player in the tracking market."

Cookies for Microsoft's Atlas service, Redmond's DoubleClick competitor, appeared on 60 per cent of the top 100 websites (compared to DoubleClick's 70 per cent). But it turned up on less than 3 per cent of the nearly 400,000 total domains examined. Omniture and Quantcast cookies appeared on 57 per cent of the top 100 and less than 6 per cent of the 400,000.