title: Show "Back to top" link element using jQuery when you scroll down
body: <p>I want to mimic behaviour with jQuery like you can see here:
  <a href="http://edo.webmaster.am/">http://edo.webmaster.am/</a></p>
  
  <p>Just look at the right bottom corner, scroll down a bit and you'll see the "back to top" button.</p>
  
  <p>So it's invisible until you scroll down a page and then it appears (animated).</p>
  
  <p>How can I do that in jQuery ?</p>