A website pop-up is a pop-up window (typically used for advertising)that contains an offer for some service or product and that appears on the screen of the website you are visiting. It usually follows you as you scroll if you do not close it or click it to take advantage of the offer. While pop-ups can dramatically increase conversion rates, most users find them to be annoying. However, when done professionally, they can be very effective. So the question about pop-ups is are they worth it?