Yes, that is possible.

• You need to write the application in Javascript, and detect somehow whether the browser is in offline mode (simplest is to poll a server once in a while). (Edit: see comments for a better way to detect offline mode)

• Make sure that your application consists of only static HTML, Js and CSS files (or set the caching policy manually in your script so that your browser will remember them in offline mode). Updates to the page are done through JS DOM manipulation, not through the server (a framework such as ExtJS http://www.extjs.com will help you here)

• For storage, use a module such as PersistJS ( http://github.com/jeremydurham/persist-js ), which uses the local storage of the browser to keep track of data. When connection is restored, synchronize with the server.

• You need to pre-cache images and other assets used, otherwse they will be unavailable in offline mode if you didn't use them before.

• Again: the bulk of your app needs to be in javascript, a PHP/Ruby/Python framework will help you little if the server is unreachable. The server is probably kept as simple as possible, a REST-like AJAX API to store and load data.