title: Visual viewport vs Layout viewport on mobile devices
body: <p>I've just read a <a href="http://www.quirksmode.org/mobile/viewports2.html" rel="noreferrer">nice article on viewport</a> which left me with a couple questions regarding Visual viewport vs Layout viewport on mobile devices.</p>
  
  <blockquote>
    <p>the width and the height of the layout viewport are equal to whatever
    can be shown on the screen in the maximally zoomed-out mode</p>
  </blockquote>
  
  <p>I did not quite understand what that means. When they say "maximally zoomed-out mode", does that mean that the layout viewport is different for different HTMLs (and not specific to different devices like iPad, Xoom, etc)?</p>
  
  <p>Secondly, I've created a <a href="http://ipad.atwebpages.com/viewport.html" rel="noreferrer">demo page</a> to measure these two viewports. (Please view this on an iPhone/iPad to get the correct values.)</p>
  
  <p>I understand that the layout viewport can be changed by setting the meta viewport tag, but that <em>also</em> changes the visual viewport--why is that? It says that the visual viewport is the part of the page that’s currently shown on-screen, so my understanding was that the visual viewport should not be affected by the meta viewport setting.</p>