Knowing the browsers and devices a web project needs to support up front can be crucial to developing a successful responsive web design. We've already considered why progressive enhancement is so useful in this respect; if done correctly, it means that the vast majority of your site will be functional on even the oldest browsers.

However, there may also be times when you need to start your experience with a higher set of prerequisites. Perhaps you are working on a project where JavaScript is essential, not an uncommon scenario. In that instance, you can still progressively enhance. Instead, you are merely enhancing from a different start point.

Whatever your starting point, the key thing is establishing what it is. Then, and only then, can you define and agree upon what visual and functional experiences the different browsers and devices that you intend to support will get.