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adCenter411 - 10:28 pm on Jul 12, 2006 (gmt 0)
You can check to see which ads are under-performing via the ad performance report. Hope that helps,
Click-through rate is also a factor, in addition to the relevancy Draconian mentioned. in general your ads will rotate equally until certain ones start to see better click-through, and then those will start showing up more often.
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