Paying for something online with a credit card is simple, right? Yes and no. Yes, because we've been doing it since the early days of the Internet (e.g. Amazon), and no, because no two credit card forms are alike.

Over the past 20 years, we've built a mental model of paying online: I pull out a credit card from my wallet, enter the card details into a web form, and click a submit button. But getting from A to Z can be a tricky journey, riddled with questions the user has to answer. And obviously, nobody wants an instruction manual.