aside.js

gistfile1.js

$(function() {
  var $window = $(window),
      $info = $('#info'),
      offset = $info.offset(),
      rightV = rightVal();

  function rightVal() {
    return ($window.width() - 960) / 2;
  }

  $window.resize(function() {
    rightV = rightVal();
    $info.css('right', rightV);
  });

  $window.scroll(function() {
    if( $(window).scrollTop() > offset.top - 36 ) {
      $info.css({
        position: 'fixed',
        top: 0,
        right: rightV
      });
    } else {
      $info.css({
        position: 'static',
        top: 'auto',
        right: 'auto'
      });
    }
  });
});