title: Center a div in a horizontal scrolling site
body: <p>Wonder if anyone could advise on the best way to center a div in the middle of the screen of a horizontal scrolling site.</p>
  
  <p>I want the header to stay positioned in the center of the screen but the rest of the site scrolls.  usually I'd just set left and right margins to zero, but as the width is set to the full scroll width I imagine I'll need to do some jQuery trickery to find the window width first of all?</p>
  
  <p>Any advice very gratefully received!</p>