I can’t recall writing about it in the past, but the way I test banners is to run them through an ad server.

I use the free program, Openads (previously phpAdsNew), to run multiple ads from competing companies in the same slots.

This enables me to eyeball the click through rates of various banner creative and companies in a controlled setting.

I combine this with data from the affiliate programs (conversion rates, average order size, etc.) to determine which affiliate programs are most profitable for me.

I like your answer, albeit a little frustrating *grins* Do you already have an article or posting which describes good testing methodology?

I think it would help a great deal to know or to see an example of how you or another affiliate (one who is actually making it) has gone through the testing cycle.