in js/theme.js [163:174]
nav.onScroll = function () {
this.winScroll = false;
var newWinPosition = this.win.scrollTop(),
winBottom = newWinPosition + this.winHeight,
navPosition = this.navBar.scrollTop(),
newNavPosition = navPosition + (newWinPosition - this.winPosition);
if (newWinPosition < 0 || winBottom > this.docHeight) {
return;
}
this.navBar.scrollTop(newNavPosition);
this.winPosition = newWinPosition;
};