Web Application testing is done on a website to check its load, performance, Security, Functionality, Interface, compatibility and other usability related issues. In Web application testing, three phases of testing is done, they are,
Web Tier Testing:
In Web tier testing, the browser compatibility of the application will be tested for IE, Fire Fox and other web browsers.

Middle Tier Testing:
In Middle tier testing, the functionality and security issues were tested.

Database Tier Testing:
In Database tier testing, the database integrity and the contents of the database were tested and verified.