Advertising has always found a way to adapt to the medium. But the introduction of the “World Wide Web” in 1991 truly changed everything—providing advertisers with an unprecedented opportunity to flex their creative chops. Within a few years, new and entirely different types of ads began to, quite literally, pop up.

The advertising industry has since come a long way. Here we take a look at some of the more interesting, innovative, and important developments that have driven changes over the past 25 years—and continue to influence digital media as new technologies take hold.