web: HTML5 Offline (IndexedDB)

Web could work in "disconnected" mode, as mobile apps, but it is more involved than standard "always connected" web pages / apps.

Offline.js – Handle your users losing their internet connection like a pro @ GitHub
Offline.js Simulate UI

HTML5 Offline Applications with Angular, IndexedDB and Bootstrap – Pluralsight Training
HTML5 Advanced Topics – Pluralsight Training

Build an HTML5 Offline Application with Application Cache, Web Storage and ASP.NET MVC @ Code Magazine
Introduction to IndexedDB: The In-Browser Database @ Code  Magazine

Can I use... HTML5 Application Cache
Client-Side Storage - HTML5 Rocks

IndexedDB - Web API Interfaces | MDN
Beyond HTML5: Database APIs and the Road to IndexedDB ✩ Mozilla Hacks – the Web developer blog
Web SQL Database - Wikipedia, the free encyclopedia
A performance comparison: WebSQL vs IndexedDB | Memory Leak