It's more of a scripting IDE than a web page and if it works correctly it will store about 5 megs of web files into an AppCache so it could work offline. You would probably need to delete/clean internet files if you want to get rid of that.
The web page is at :
At the top left (if it works correctly) you will see status for LS (local storage), IDB (indexedDB), and AC (AppCache) ... the appcache should show downloading and then idle.
Can someone test and let me know what the status information of LS/IDB/AC are.... or if you use it, how well it works? There's a samples browser button (second from right under help) if it lets you load all the samples.