Originally Posted by Markul

Here is the thing about ad networks CPM rate and publisher sites:

If you have one site and your CPM drops, it's (usually) because high bid advertisers filter our your site because it's not converting. This means you get paid for run on network campaigns, that pays MUCH lower than targeted campaigns.

OR.

A media buyer that was buying up large volumes of traffic that your site had (GEO, type whatever) stopped bidding so much or all together, your CPM will drop.

You can then move to a different network and see what happens there, probably the same thing. That's why you want to run "many" ad networks on many sites to constantly optimize your zones as a publisher.

Or just live with a lower CPM and stay in one spot, where the CPM will go up and down. If your CPM stays crappy with a network, it's probably because your traffic is crap and then you need to improve your traffic generation methods.

Just my