The demos seem to work fine for me at the moment and my best guess is that there has been a temporary downtime (e.g., an application pool recycle) when you attempted to access the demos.
Could you try them again and let me know if you continue to experience issues?
On a side note, you can download the demos project from your account so you can run them locally. This provides you with the following benefits:
You do not need an Internet connection to explore the demos.
You can examine and modify their code at your leisure in your IDE.
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