ishans - 11:29 pm on Jul 18, 2006 (gmt 0)

Hands down Google will bring in the bulk of your traffic thus the resulting number of conversions (if your site is converting that is . . .). Overture/Yahoo will be your second and MSN adcenter third, again due to the amount of traffic they will bring in through the PPC ads - in my opinion this is due to the design layout on the respective search pages (but I digress . . .). It would be an interesting exercise to note that even if you have an equal dollar value allocated to all three ad-platform campaigns, and use the same keywords/ads on all 3 engines you will see your spend split - that will essentially be your optimum allocation. Thus I would start with keywords focused toward your site strength or highest converting keywords to determine your spend ratio, I would then expand on my keywords and test secondary keyword campaigns on each engine while maintaining your budget allocation accordingly.

Ishan