$(document).ready(function () {
	var $nav = $('div.main-nav-holder');
	var base_top = $nav.offset().top;
	var docked = false;
	var $window = $(window);
	$(window).scroll(function () {
		if ( !docked && ($nav.offset().top - $window.scrollTop() < 0) ) {
			$nav.addClass('docked');
			docked = true;
		} else if ( docked && $window.scrollTop() <= base_top ) {
			$nav.removeClass('docked');
			docked = false;
		}
	});
});