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The reason I ask is because my pages containing Ad Links and standard AdSense units are currently showing fairly significant differences (around 10%) in the page impressions for the two styles, and with every page having both styles, the impressions should be the same.
I have many pages with 120x90 and 300x250 recorded in seperate channels.
The channels with the 120x90 AdLink shows always higher numbers.
I assume this is because
An AdLink showing search for ads counts as an impression
A 300x250 showing my PSA replacement does not count