MikeNoLastName - 8:58 am on Sep 13, 2007 (gmt 0) [edited by: MikeNoLastName at 9:06 am (utc) on Sep. 13, 2007]
OF COURSE your OVERALL eCPM is going to tank if the CPM for the downed site was inherently lower than the other (up) site (duh - since you're averaging the two together). That doesn't mean the down domain is useless. It may still be making you significant money independent of the other domain. What you need to look at however is whether the specific CHANNELS for the up domain ALONE were affected. Hopefully you had enough URL channels defined on the up domain before and after the down time to get a statistically significant sampling to determine this. A week, should just be sufficient if the traffic is high enough. If the PPC and eCPM for the up channels ALONE were affected negatively while the other was up and positively while the other domain was down, THEN and ONLY THEN, might you consider to vanquish the down domain ads.
On the other hand, I too have noticed overall advantages to "weeding" out certain individual high traffic pages on ALL domains which had particularly low CTR/eCPM and directing visitors to closely related well-paying pages.
[edited by: MikeNoLastName at 9:06 am (utc) on Sep. 13, 2007]