“We’re better connected than we’ve ever been, but we’re not always connected. ApplicationCache lets users interact with their data even when they’re offline, but with great power come great gotchas. For instance, files always come from the ApplicationCache, even when the user is online. Oh, and in certain circumstances, a browser won’t know that that the online content has changed — causing the user to keep getting old content. And, oh yes, depending on how you cache your resources, non-cached resources may not load even when the user is online.”