title: Redirect mobile devices to alternate version of my site
body: <p>We've got an alternate version of out website ready for mobile devices. The content we serve is different and it works well. </p>
  
  <p>What is the best way to detect which version to serve. We don't have a list of all mobile devices so to use the user-agent header is tricky as we may miss something. </p>
  
  <p>We thought about useing device screen width - but what happens if the mobile device doesnt support javascript. How do we sniff this ? </p>