title: HTML loading page à la blogger.com
body: <p>I'm trying to determine the cleanest way to implement a brief loading screen that would be displayed to my site's visitors while JavaScript is loading some data behind the scenes, processing it and updating the DOM accordingly.</p>
  
  <p>I like what blogger.com does with one of its themes, specifically <a href="http://blog.datomic.com/" rel="nofollow">this one</a>. It seems to completely fill the screen with a grey background with a spinny image on top, and then it fades out once all the underlying work is completed.</p>
  
  <p>Does anybody happen to know how exactly they achieve that effect? I haven't gotten too far with just poking around in Firebug. Doesn't look like it's being hidden or removed from the DOM.</p>
  
  <p>Thanks!</p>