Keep an offline message in the browser . Gmail , YouTube etc

Question

When the internet connection is unavailble, and we try to browse to Gmail when it had opened earlier, a message can be seen:

Gmail The app is currently unreachable.

This same way also with Youtube.

In the Gmail offline message, I saw this attribute in the body tag:

jstcache="0"  

How can we implement such a page when the page/browser is offline ?

Answer 1

They're using offline browsing, another new feature in the HTML5 spec. Take a look here: http://diveintohtml5.info/offline.html

It enables you to define certain assets on your site, using a manifest, that are cacheable. The browser will save them and display accordingly whenever the user is offline.