Online adverts should be like magazine adverts: static text, an image, no video, no sound, no animation, and stuck where the printer put it.
If I read a car magazine, I expect car-related ads. If I then read a gardening magazine, I'd expect gardening-related ads, not car-related ones.
If I buy an item, I don't want to see adverts for the same thing for weeks after, it's pointless. If I have bought one, chances are don't I need another And if I do, I think I could find it again without seeing adverts plastered all over.
Until online advertisers become responsible and trustworthy, I'll stick to blocking ads. If a website insists I have to see them, I'll find another site.