Pop-ups, if you’re somehow, strangely, not familiar with the term, are those little windows that open when you visit certain sites. ** Generation One - The Pop-Up Until a few years ago, the pop-up was considered the biggest breakthrough in advertising on the web. When they were first introduced they were a great success and click-through rates went through the roof. Imagine being able to interrupt whatever your visitor was viewing, by launching a secondary window on top of the browser windo.