Within the mobile computing sector, web applications are different from native applications which are
developed for a particular platform or device and installed on that device. The two are not mutually exclusive
because many applications contain elements of both native and Web application. A web application can be
divided into three different layers. Presentation layer which forms the first tier of the application consists of
web server and the web browser, which is responsible for assembling the data into presentable format. [5]
Application layer constitutes the second tier of the application and is consisting of server side program and
scripts. Finally the third tier provides the programmable access to the databases. When a user which is first
tier, send a request to the web server, web server process the request which is second and third tier, formats
the result and finally sends the formatted results from first tier to the client. In this process server side scripts
play a very important role of processing the users request and in the generation of dynamic pages, based on
user and its input.