Ads on phones
Ads on webpages on phones are very annoying they fill up the 5" screen and you need a pin to close them. Otherwise closing the ad with your finger you start opening up Google Play, or AppStore.
the youradchoices adverts tend to be particularly annoying. "remember that office chair you looked at 3 months ago?" , "no?" , "well here are more charis for you to look at"