title: How to make div scroll down with a page once it reaches top of page?
body: <p>I know title is a bit confusing ;D but basically what I want to do is clearly demonstrated on this website <a href="http://9gag.com" rel="noreferrer">http://9gag.com</a> scroll down and pay attention to sidebar, there are 2 advertisements once 2nd advertisement reaches top of the page it starts scrolling down with a page.</p>
  
  <p>I would like to know how to do this? html/css or jQuery solutions are prefared.</p>