Are your unique visitors truly unique? As many as 39 percent of online users delete cookies from their primary computer each month, according to a new Jupiter Research report. The survey referenced in this report found 12 percent of consumers delete cookies monthly; 17 percent weekly; and 10 percent daily.

This indicates traditional unique visitor counts are increasingly inaccurate, and possibly irrelevant.

It's imperative to understand this trend's effect. A user deletes or rejects a cookie. When she returns to the site later, she's registered as a unique visitor. An inaccurate unique visitor count can potentially skew the accuracy of your Web analytics metrics, including information you may be using to sell advertising or maintain relationships with affiliates. In previous columns, I've discussed the importance of having accurate data for decision-making.

Look at the data from your Web analytics tool. If you have fewer returning visitors and more new visitors when nothing else has changed in your business, you may be experiencing the effects of this cookie blocking and deleting trend. All our clients experience it, and an increasing percentage of their site visitors aren't accepting cookies at all.

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