title: Support of different Javascript versions in browsers
body: <p>Surfing the MDC docs <a href="https://developer.mozilla.org/en/JavaScript" rel="noreferrer">here</a>, I've noticed there are quite a few versions of javascript (1.6 to 1.8.5).</p>
  
  <p>I was wondering:</p>
  
  <ol>
  <li><p>Is there any online reference for Browser / Javascript version supported ?</p></li>
  <li><p>Is there any practical application for the use of different javascript versions ? According to MDC you need to do something like this to use them:</p></li>
  </ol>
  
  <p><code>&lt;script type="application/javascript;version=1.7"/&gt;</code></p>
  
  <p>Which I haven't seen in any website IIRC.</p>
  
  <p>Thanks!</p>