In previous chapters, we have considered briefly the notion of progressive enhancement. It's an approach to development that I have found so useful in practice I think it bears repeating. The fundamental idea with progressive enhancement is that you begin all your front-end code (HTML, CSS, JavaScript) with the lowest common denominator in mind. Then, you progressively enhance the code for more capable devices and browsers. That may seem simplistic and it is, but if you are used to working the other way around; designing the optimum experience and then figuring out a way of making that thing work on lesser devices/browsers, you'll find progressive enhancement an easier approach.

Imagine a low powered, poorly featured device. No JavaScript, no Flexbox support, no CSS3/CSS4 support. In that instance what can you do to provide a usable experience?

Most importantly, you should write meaningful HTML5 markup that accurately describes the content. This is an easier...