The JSX in the react-router examples uses "class" instead of "className", and with the current version of react (15.4.1) the "class" declarations are ignored. The most obvious impact of this is on the nav bar, which is rendered as a simple list of links. Although there is an npm package named jsx-html-class that will allow the use of "class" in JSX, I don't recall seeing it mentioned during the setup/configuration portion of the tutorial.