- Flash ads
- Video ads that waste my bandwidth (though I guess a minute of ads while watching a show is better than the 15 minutes of ads on television)
- Pop ups.
- Basically any ad that is intrusive (in other words, gets in the way, or distracts me from what I'm doing).
I think it varies depending on how high value the advertisers think you are.
If you are in what they consider to be a low value country, on a mobile or are generally worthless to them (e.g. unlikely to convert on that promotion for a flight), then they tend to serve you trash adverts.
Incidentally, the people who never tend to click on ads also tend to be the ones who get worse ads and I would imagine that they check to see if you actually follow through with an actual purchase.
Mostly websites cluttered with ADS. I understand that website owners need funding but god damn some are overboard and it’s enough for me to leave the website!
Video advertisements on sites that are already overloaded with other crap. It just makes everything run so slowly.
Pop-ups are annoying but they're usually easy to avoid with an ad-blocker. The ones built into the site that ask you to register or whatever are fine, so long as it doesn't do it on every single page after I've already said I'm not interested.