Offline Fallback
Objective: To display an offline page when the network can't connect.
Switch off the network connection and refresh this page to see what it looks like "offline". (Hint: it involves cats).
To work offline in Firefox, simply select File > Work Offline.
In Chrome, you can simulate a disabled network using the Developer Tools. Under the Network tab, select Offline (0ms, 0kb/s, 0kb/s).