I guess I'm not using GM then.
Probably not an issue, could slam something neat up with three.js, and if I'm entirely honest, JS makes life easy enough that you really don't need most of the things GM provides.
@puke:
GM uses AJAX to load its resources, and by default, browsers don't allow AJAX requests to the local disk, even if it's just in the same folder or subfolder.
Savestate's answer fixes that -- but it's not something you'd suggest for distribution, it's strictly for dev purposes before you host it somewhere.
The game doesn't need to be on the internet to run, it just needs to not be seen as on the local machine by the browser.
admittedly, GM's HTML output was meant to put on actual sites -- you'd just provide a download for a native version for your OS if you intended to play offline