The thesis presents a description of the steps involved in designing and evaluating the usability of graphical user interferences. It presents in detail Norman's heuristics, Fitts's law, cursor guiding task, Mandel's golden principles, Nielsen's principles, design guidelines and usability dimensions. Heuristic evaluation and user testing are described theoretically and are furthermore presented by providing practical examples too. The guidelines and principles are included in a programming tool for assistance in designing and evaluating graphical user interferences that were developed and tested. The programming tool was created in the development environment NetBeans combined by Java, Swing and HTML. The programming tool performed well in practice. We used it to draw up an example of heuristic report and a user testing report of evaluating the user interface of the Clicktrans application
