As mobile devices become more and more diverse and ubiquitous, but network connections still cannot be relied on at all times, a new challenge arises for all those who are developing web applications: What if your user gets disconnected from the internet? How will your applications react? Will they just fail showing an error, or will they still be usable? What does it take to make a web application offline-proof? This talk will give insight into proven user experience patterns, how to solve issues like caching files and storing data offline, as well as into current technical limitations.