How to fix menu?

var navPos = $('#main-navigation').offset().top; $(window).scroll(function(){ if ($(this).scrollTop()>=navPos) { $('#main-navigation').addClass('fixed'); } else { $('#main-navigation').removeClass('fixed'); } });

#main-navigation.fixed { position: fixed; top: 0; left: 0; right: 0; z-index: 10; margin-top: 0; }