Unfolding intrusive advertisements
Imagine that you visit a website and accidentally move your mouse over a large advertisement there. It unfolds automatically, becomes bigger and takes over the content you are trying to read. The only thing you can see now are where most of the text lines start and with which characters. This is exactly what happened to me. Annoyed that reading was hindered, my first reaction was defensive, so I immediately tried to cancel this advertisement. But this time I had to actually click on the close button to contract it to its original state. So I did that, unaware of how it was smarter than me to appear above the content at first. But then, my cursor remained on the text, which while reading is still inconvenient. So I tried to set it aside too, hovering again unintentionally over the same ad. After it unfolded slowly for the second time, something in me "clicked". So the ad didn't receive a third chance.
Here I speak about a news site with a relatively big audience. This is a clear example of intrusive behavior that breaks user's expectations. And it imposes a usability problem too, since you can easily activate, but hardly deactivate the ad. In the first case you don't even need a click, while in the second—a click on a tiny area is needed. If you point your mouse slightly away from the close button and click, you go to the advertiser's page, but if you don't risk that, there's no way to read the content you came for. If you use ads on a web site, please make sure that they don't interfere with user's intentions. No one wants to be tricked in any way.