An ad is an ad, and we accept them to some extent, and we usually want to close them as soon as possible. Still, what makes an ad particularly irritating is when:
- The ad is a modal that cannot be simply ignored while using the app - The X button is hard to detect (faint, small, or in an unusual place) - The amount of time to wait until you can exit is ambiguous or unknown
Essentially, the increase in cognitive load pushes the user to stop focusing on closing the ad, and instead, to lose concentration the rest of the page so that it all be funneled to the ad. This breaks the flow of the user's activity outside the modal. While advertisers have a reason for that strategy, it shouldn't take place on a normal website flow.
More text-based [autocompleted] input rather than dropdowns works great for things like countries (I see more job applications with autofill input for city, state, and country to be filled in at once rather than multiple text boxes/dropdowns). I also like the idea of an animation for modals from top to bottom, so long as it is not slower than the pace the user would read the options.