This is important to get consistent sizing and scale across different platforms. The meta viewport tag simply insures that the window is sized correctly on whatever device it runs on.Replace this with jQuery if you so desire. It is not a dependency for App.js but still nice to have for writing concise, cross-platform code. zepto.js is jQuery-like library focusing on being lightweight and mobile-friendly.It contains iOS/Android styles for all included widgets. default.css is the default stylesheet provided with App.js.app.js is the core module containing all library functionality.This is the preferred structure of your HTML when starting an App.js webapp.