Turn off Application Cache with manifest

In Chrome, go to Under the bonnet -> Content Settings -> Cookies -> Show cookies and other site data, application caches should show up under the site data.

In Firefox go to Advanced -> Network, sites with application caches are listed in a box at the bottom.

There's no way completely to completely remove or expire an application cache from the server side at present. The best you can do is explicitly tell the browser to remove all the cached files - a manifest with just a network section should delete all the other files, but the file with the manifest reference will itself always be cached.

--edit

This answer is no longer entirely correct. Currently the standard states:

If fetching the manifest fails due to a 404 or 410 response or equivalent...Mark cache group as obsolete. This cache group no longer exists for any purpose other than the processing of Document objects already associated with an application cache in the cache group.

That is: deleting the manifest file should cause the appcache to be deleted the next time the browser attempts to update

Delete the manifest file in your development computer.

You can disable the application cache in Chrome via the "--disable-application-cache" command-line switch (this is in the dev channel of Chrome, using a linux build... but I'm sure it's the same in the beta/standard channels, and for other platforms):

google-chrome --disable-application-cache