title: what will block a request of the browser?
body: <p>As i konw, if connections between browser and the server is used up,the request will be blocked .<br>
  i read <a href="http://www.stevesouders.com/blog/2010/02/07/browser-script-loading-roundup/" rel="nofollow">http://www.stevesouders.com/blog/2010/02/07/browser-script-loading-roundup/</a><br>
  js will block the page render ,it won't be parallel downloaded with some other resource like image,iframe(different between browsers)<br>
  my question is:</p>
  
  <ol>
  <li>is there any other condition will make it?   </li>
  <li>is it means js will block the request for iframe?  </li>
  </ol>
  
  <p>expect your help! 
  thanks  </p>