[wenham]

For those that don't want to, and 'miss the point'. View source and go to the .JS file

The text of the off-line site is about a third of the way down.

[SparkyMcUnicorn]

Or chrome dev tools -> toggle device toolbar on -> switch "Online" to "Offline".

Or run in your console: window.dispatchEvent(new Event('offline'))

[Insanity]

Yup exactly what I did :D