hi i was wondering how much meta tags play a role in which ads are displayed in the adsense blocks. i assume not too much for content pages, but what about pages that lack in content????

Doh! You can't (or shouldn't) put it on pages without any content, good way to get banned from adsense for life if you do though. The ads displayed relate to the keyword density of your site, stuffing it full of meta tags will have no effect to the best of my knowledge.
The only way you can run adsense on a site with no content (Again to the best of my knowledge) is to use "Adsense for parked domains". Other than that - adsense+no content = ban at some point soon.
Hope this helps, wouldn't like to see you lose your account.
Dickie