Today the competitive online market requires a web application to be user-friendly and intuitive. Following usability principles during the application development process is a key for application to succeed. That’s why usability principles should be learnt and followed by the whole development team. The goal of the thesis is to conduct the usability testing and improve an enterprise web application for Good Sign Oy in order to increase the quality of the product and enhance customer satisfaction with the product. The project includes full usability testing lifecycle and the process of findings implementation