Does Google have any policies (even vaguely worded that might cover this) that relate to the quality of a page that adsense ads are shown on? By this i mean, can accounts be terminated due to poor design, incorrect information and so forth?
To be brief: Poor design - No Incorrect information - No If someone has wrong information on their site, they should do more research or choose a different topic altogether and leave it to someone else. You might get banned if you're caught using hidden text in order to pull more relevant/high-paying ads. Of course that is a separate issue from adsense and will only lead to your site being deindexed from the SERP's instead of getting banned. Just my $0.02.
Well. if the pages are poor in the way that is harming google's integrity and violates its T&C, you are doomed.
I have read that the ad pays different depending on the quality content on the page. Smart Pricing, they check how relavent the content of the site is to the ad they are displaying.. I saw this one month when i had the same amount of clicks, but i did not have any ££££. (not sure if this is the reason or i had a bad month)