Anyone comparing PPC and content ads? I've got a series running on a popular site, and have targeted some keywords, yet G hasn't given me any impressions on the PPC. The site-targeted ads ran up short of 300 impressions before I replaced them with some others, as I hadn't got a single click through!...

Any tips, ideas, suggestions?
If it helps, my aids are for a charity

Im not sure what you mean exactly.. are you talking about the link unit when you say PPC? (the content ads are also PPC..?)