Removing HTML5 Offline AppCache

In modern Firefox you can manipulate the offline cache with Edit Preferences Advanced Network.

In windows it is now (v27.01) Tools Options Advanced Network

You simply need to remove the appcache manifest from your server. If the browser can't access the manifest file, it will stop caching your app and remove all cached data.

Some useful information from two sites:

If the manifest file itself can't be retrieved, the cache will ignored and all cached data associated with it will be disregarded.

http://appcache.offline.technology/

Application caches can also become obsolete. If the manifest is removed from the server, the browser removes all application caches that use that manifest, then sends an "obsoleted" event to the application cache object. Then the application cache's status is set to OBSOLETE.

https://developer.mozilla.org/en/Offline_resources_in_Firefox

Manually delete app cache: Only for Chrome

Enter the follow URL in your chrome browser: chrome://appcache-internals/

There you will see a list of every application cache you have in storage with the possibility to remove any of them.

Reference

FOR anyone coming across this question and who've deleted the appcache manifest, deleted the browser's cache and removed the manifest from the server and the reference to it in the HTML: If this still did not cause your HTML document to load the update version in Google Chrome, you can go to chrome://appcache-internals/ in your browser and click REMOVE next to the manifest you wish to get rid of.