title: Position fixed when scrolled passed certain amount of pixels
body: <p>I'm looking for a way to position the #header element of my page as "Fixed" only after having scrolled downward for about 170 pixels.</p>
  
  <p>Above the header is a banner, so when people scroll down, I would like the banner to scroll away, the header to stay fixed when it hits the top of the window, and the page content to scroll underneath the header.</p>
  
  <p><a href="http://jsfiddle.net/tdskate/zEDMv/" rel="nofollow">http://jsfiddle.net/tdskate/zEDMv/</a></p>