HTML 5 Offline Application can be difficult to troubleshoot because you tend to see app cached manifest data, not the latest.
There are at least 2 ways to help:
- Use Chrome’s Incognito mode so it always loads things from scratch.
- chrome://appcache-internals/ and Remove the appcache
Of course, the easy way is just comment out the html tag manifest during development. Enable manifest only when you want to test the offline scenario.