Running Firefox 45.02 and downloaded the newest Babylon.js and the Samples last night. After unzipping into local folder, I get "Error: WebGL not supported" when doing any of the demos. It works great on the actual website, but not on localhost from the files on Github.
I then tried uploading it to a web server, and get the following errors when trying to access the demo Samples-master/Demos/AdvancedShadows/index.html:
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Samples-master/css/index.css"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Assets/CamTouchOff.png"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Assets/CamVirtualJoy.png"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Assets/CamGamepadJoy.png"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Assets/CamDeviceOff.png"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Assets/camera.png"
"NetworkError: 404 Not Found - https://cdn.xxx.com/Babylon.js-master/Assets/CamAnaGly.png"
In particular the index.css file seems to be missing from any meaningful directory as line 18 of the index.html has this line:
<link href="../../css/index.css" rel="stylesheet" />
That doesn't point anywhere as the only index.css files are in subdirectories of the Samples-master directory such as the CYOS directory.
I am just experimenting with Babylon.js as a replacement to Three.js and am dissappointed that you can't seem to unzip and use anything. Here is what my directory structure looks like and you can see all the PNG files listed in the errors above are indeed missing for some reason.