What is a viewport? You may have seen the meta-tag named "viewport" on newer mobile-friendly websites. The mobile (iOS) version of Safari introduced the "viewport meta tag" and "scale" on the viewport for mobile (scale optionally being one of the special values minimum-scale, maximum-scale, and user-scalable).
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
A viewport is like a logical window. You are on one side of the window looking through to the...