incrediBILL - 1:38 pm on Apr 27, 2010 (gmt 0)
I went digging in AdBlock for FF since it seems to be a major issue.
Here's the deal, if you run AdBlock with the default EasyList out-of-the-box it blocks AdSense but doesn't block Analytics, therefore it could theoretically contribute to a lower CTR, but it may not, read on...
Also, if someone is running AdBlock they can add their own rule with .google-analytics.com or subscribe to a privacy list containing GA installed, then it blocks Analytics as well so that visitor would be invisible and not even be included in the stats.
But out of the box, the GA will record this visit, AdSense doesn't show, so AdSense itself WOULD NOT COUNT this AdBlock'd page toward their CTR since there is no impression.
The question is, would GA attempt to resolve this situation since GA knows there was a page impression which AdSense didn't count and adjust the CTR according for GA reports, or just show the raw data collected by AdSense?
This is a key to knowing exactly what were looking at in GA's browser AdSense stats because counting AdBlock'd pages or not makes a huge difference in what this stat really means.