Earnings can vary based on a variety of reasons. We do not have a set rate for advertisers, so the earnings you receive can vary widely based on several different scenarios:
1) Advertisers Bids: As we are a live bidding platform, advertisers bids can vary widely. We have some advertisers that are bidding high for traffic one day, and the next day the same ads can pay less. We optimize the ads displayed on your site to ensure the maximum possible earnings, however some days will pay less or more than others.
2) Traffic Geos: Where your traffic is coming from plays a major role in how much you will earn. Traffic from tier 1 traffic tends to pay the most (Though not always). The lower tier traffic you have, the less you are likely to earn. For example, if you have 99% traffic from India, you are less likely to earn as much if your traffic was from the US, or another tier 1 country.
3) Advertisers displayed on your website: Some advertisers may whitelist your site if it converts well for them, however some may block your site if it does not. This does not mean you have bad traffic, it just means that the ads they are displaying may not work well on your particular site. Its possible you may see an earnings drop because your site has been blocked on a particularly higher paying offer. You won't know if you are being blocked or not, however it is certainly a possibility if you see a significant drop in earnings with no decrease in traffic or clicks.