Piperka uses Comic Ad Network for advertising. As the name implies, they're an ad network that focuses on web comics. They don't try to profile or track you either but collect just simple impression and click statistics.
Still, in the spirit of letting you control what's running in your own browser, I'm giving you the choice of opting out of them. Though I recommend to just leave them be, you may even see a web comic that'd match your interests on them.