Offline.js is a library to automatically alert your users when they’ve lost internet connectivity, like Gmail. It captures AJAX requests which were made while the connection was down, and remakes them when it’s back up, so your app reacts perfectly.
It has a number of beautiful themes and requires no configuration. The library is plug ‘n’ play with no setup and it comes with multiple good-looking themes. It has been tested on Modern browsers like Chrome, Firefox, Safari and IE8+.Offline.JS