Hey there) You know it,s common and usual to see a Forex related ads on a dating site because just dew days ago you visited some sites about Forex trading .Adsense not just render ads based on a site content but also use user browser for behavioral targeting . So for example i run a politics forum but a user who visited previously visited some dating sites ,saw a adsense dating ad on my site he clicked on it and i got my pay per click earning .the question is it common for adsense publishers to get adsense earning to keywords outside of their niche and site content ?Suppose adsense ads for my site content have lower pay per click rate but can i get a higher pay per click earning just because some of my site users were previously visited sites with a higher pay per click?
It Depends, if you have a good content with obvious niche, google will find a relative ads for your content but if google doesnt have any ads/advertisers related to your content, it will show other ads related to the past search of the user.