I have several sites. Usually the page impressions are somewhere in the ball park as the number of visitors for that day. However, my one site gets 500-600 visitors daily but only 50-100 page impressions. This seems abnormal to me. Does anyone know possible reasons for this?
You just posted this on warrior forum. Same answer. Use Google Analytics, Webmaster, and Your Hosts stat tools to see if you are getting real visitors or just bot traffic and "hits".
Could be because adsense doesn't have ads to show for many of your pages, so you have less ad impressions than visitors. Show us the url and it'll be easier to point out problems.