Fixed Navigation on oscon.com/oscon2013

fixed-nav.js

var headerHeight;
// is navigation visible? See #en_header with height 150px, so when scroll down more than 150px, we make the #nav_borders position fixed.
$(function() {
  headerHeight = $('#en_header').height() + 1;
	$(window).on('scroll', fixNav);
});

// if not visible, then make it fixed
function fixNav() {
	if ($(window).scrollTop() >= headerHeight) {
			$('#nav_borders').add('#headlining').addClass('fixed');
	}
	else {
		$('#nav_borders').add('#headlining').removeClass('fixed');
	}
}

fixed.css

#en_header {
  height: 150px;
}
#nav_borders.fixed {
  position:fixed;
  top:-1px;
  _position: absolute; /* ie */
  _top: expression(eval(document.body.scrollTop)); /* ie */
  z-index: 100;
}
#headlining.fixed {
  padding-top: 26px;
}