HTML5 adds number of new features and technologies to allow developers to build rich and immersive web applications. One of the features introduced is the "LocalStorage" that allows web applications to store data in a "persistent" fashion in a client (browser) side store.
Foundstone HTML5 Local Storage Explorer is a Firefox extension that allows for viewing, modifying and deleting of data items stored in the browser's LocalStorage.
It also allows the user to copy the contents of the Local Storage to clipboard.
You can download and install the extension from:
Here's the menu bar button that can be used to invoke HTML5 Local Storage Explorer once it is installed
Here's the main screen which displays the contents of the Local Storage. It allows emptying the local storage, refreshing its contents, copying its contents to clipboard, view the version and developer information and closing the add-on window