title: How reliable is detecting mobile devices by screen resolution?
body: <p>This sounds a bit too good to be true, so please tell me if it is.</p>
  
  <p>If I have just one single version of a mobile website (no variations for
  different devices, just one website for all mobiles), how reliable it is
  to detect mobile devices by screen resolution?</p>
  
  <p>And simply serve the mobile version if screen resolution is &lt; than say 400px.</p>
  
  <p>NOTE: My question assumes that javascript is enabled. Also,I'm aware there's
  user agent detection, but I'd like to do without it.</p>