High Performance Browser Networking: What every web developer should know about networking and web performance

Michal Zalewski’s The Tangled Web: A Guide to Securing Modern Web Applications

Jakob Nielsen’s Usability Engineering and Steven Seow’s Designing and Engineering Time are both excellent resources that every developer and designer should read! Time is measured objectively but perceived subjectively, and experiences can be engineered to improve perceived performance.

The application can subscribe to navigator.onLine notifications to monitor connection status. For a good introduction, also see Paul Kinlan’s article on HTML5Rocks: Working Off the Grid with HTML5 Offline.