If you can see this, React is not running. Try running:
npm install -g babel cd examples/basic-jsx-precompile/ babel example.js --out-dir=build
This is written with JSX in a separate file and precompiled to vanilla JS by running:
npm install -g babel cd examples/basic-jsx-precompile/ babel example.js --out-dir=build
Learn more about React at facebook.github.io/react.