It argues for a mobile-first approach to web development — by building for small screens first, then using @media queries to “size up” the experience and adapt your content on the fly, you can make sure people see the best version of your site for their particular device. It makes the most sense on the mobile web, where viewports and browser capabilities vary widely, and where (as Rieger points out) our definition of what exactly is a mobile device remains open. It’s an extension of the old “progressive enhancement” approach from the first decade of the web.
There are also some great data breakdowns about devices and browsers at the beginning. The takeaway: We’re all developing for Mobile Safari and Android, but most of the world is still using something far less advanced to visit your site.
Of course, the browser audience will vary based on the content — here at Wired, most of our mobile visitors use iOS devices, and the bulk of the rest use Android. But for a non-geeky site, things will skew more towards mobiles with clunky browsers.
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