It is recommended to use a local sever when developing. If you are on Windows, you could use WAMP or a Python server.
You can install WAMP from here.
To see the site, put the website folder inside your WAMP installation's www folder.
This implementation uses the Application Cache API. There is a file called offline.cache. This configuration file tells the browser which files to cache for offline support.
When a change is made to the JS, CSS, or HTML, the browser's cache won't be updated. You must modify the offline.cache file. A simple change you can do is to change the time in the Version comment.