Web App: High Availability / How to prevent a single point of failure?

In simple words high availability can be defined as running a system 24*7 without a downtime even if there are hardware and software failures. In other way a fault tolerance application. This helps ensure uninterrupted use of the application for it’s intended users.

Read more on High Availability Deployment Architecture

I have found this article on the subject: http://www.tenereillo.com/GSLBPageOfShame.htm

Basically if you do not require long lasting sticky sessions you can configure your DNS servers to return multiple A records (IP addresses) for your website.

Web browsers are smart enough to try all the addresses until they find one that works.