One of the advantage of web apps is that you can access all your information on the go, but if you don't have an internet connection in some situations like when you are in a plane, train or carpool you are alone, you cannot access these apps. But, now Google has come out with a solution as Gmail Offline app for Chrome. Now you can access your Gmail even if you don't have an internet connection.
With this HTML5 powered app you can read, archive, respond to and organize mails without having an internet connection. You cannot send and receive emails with this app. You can save your composed messages in draft and can send when you get an internet connection.
This app is available only for Chrome browser .You can download it by going to the Chrome Web Store. After downloading and installing this app you can access it by opening the new tab. You will see the icon in the new page in new tab.
Update: Improvements In Gmail offline Chrome app