title: HTML/CSS - Fixed Backgrounds while scroll
body: <p>Any idea or explanation how they did the backgrounds of this site?
  <a href="http://upcircuit.org/" rel="nofollow">http://upcircuit.org/</a>
  Basically, a fixed background is the trick here.
  But there are multiple backgrounds and I am trying to solve the tricks of this site :))
  I tried scanning the page source but I have no idea how they did this.</p>