But it's not your website. It's someone else's. Someone who created the content and pays to keep it online for you to consume.
Is this ethical? It's not illegal. But that isn't the question.
But if every time you visit the museum someone follows you around talking in your ear about the products available in the gift shop, you might choose not to go, or (if the content is interesting enough) you might start wearing headphones or earplugs and go anyway.
Certainly.
> and how you use it
Now that's an interesting question. I wonder if we'll start seeing people try to use explicit copyright licenses to say that your license is revoked if you use an ad blocker. Not sure what that'd look like.