I have had a little success with site targeting, and was wondering if anyone knew the answer to the following... Essentially, I have to bid more than the CPM the site is making off of PPC ads to display. So, if a site's normal adwords are earning them $5CPM, then I need to bid over $5 CPM to display... right? But over what length of time is this cpm calculated? If a site for a month has a cpm of $5, but due to a traffic burst is suddenly only making $1 CPM for a day, when will my $2 CPM be triggered, if ever? Know what I mean? If a site gets to page 1 of digg or something, it's CPM will go way down b/c virtually no one clicks on ads. Can I jump in when their CPM is artificially low due to a traffic spike and get my ad displaying at a low CPM.... then hold it when traffic returns to normal? Or, is the calculation based on a longer period of time?
No one knows the "for sure" answer to that except G'. Based on what I've seen, those "spikes" in the up or down direction do not have an immediate impact on the CPM you pay - it's averaged over some unknown length of time.