My app is a webapp (rather than a blog or video site). The traffic is a mix of Vietnam, Brazil, Mexico, Colombia, and about 10 other countries. The number of pageviews in February was 2.6 million and the number of monthly uniques was 450,000 (March is 350k so far). What ad network should I use? The users are on desktop web browsers.
You can test a popunder ad from AdMaven, so that way you don't have a banner that takes place from the app.
Conversely, if you are interested in displaying brand safe friendly banner ads which are purchased directly from the advertiser then try AdClerks.com You can then monetize any unsold ad space with SwiftAds.
It depends on how intrusive or polite you want to be with your user base. Definitely more intrusive formats, such as popups (from zeropark, adcash, propellerads...) will give you higher earnings. A more sutil approach, and will help you keep your userbase around longer could be banner such as adsense banners.
From my experience, I would advice you to go for Adnow . Ad now is the easiest to utilize and they offer high CPC.