What is difference between web application post implementation and pre implementation?

Pre-System Implementation Reviews cover the evaluation of project management practices, design of control structures and security requirements, participation during IT system testing, validity of data conversion, audit of system interfaces, and general controls surrounding new or modified systems. Such implementation reviews provide a cost-effective approach to the enhancement of controls and security of the applications before systems are implemented into a production environment.

Post implementation includes addressing risks associated with new and modified systems that are already being used in a production environment. These IT system audits ensure that systems are operating as intended, meeting expected business objectives, and that the security and general controls surrounding the applications are adequate.