Pop ups can easily annoy visitors if they cover the screen or appear too often. It is better to show them after a few seconds or when someone has scrolled a bit, instead of immediately. The design should be clean and easy to close, especially on small screens. Keeping the message short and clear also helps. For example, a small pop up offering a discount with a clear close button feels less annoying. You can also limit how often it appears for each user. What kind of pop ups do you think people tolerate better on mobile sites?