Graphical user interface (GUI) has become the key element of modern information systems and is commonly viewed as one of the decisive factors for the success of an information system project. To help develop effective GUIs, many tools have been introduced by software vendors to meet the needs of designing a variety of interfaces. Such modern design tools offer system developer vehicles to create sophisticated GUI with a few codes. However, the complicity of many GUIs and the varying expectations among users, designers and developers make the communication among them and the use of most prevailing design tools a real challenge. An integrated tool for better design and development of GUIs may help alleviate the problems caused by the mis-communication and the knowledge gaps existing among users, designers and developers. In this paper, a new design tool, which integrates the GUI design techniques embedded in Unified Modeling Language (UML) and the Presentation-Abstraction-Control (PAC) model in Web environment (Net-PAC) is proposed. The potential problems of using vendor-provided design methodology will be presented. Special features of the proposed integrated tool will then be discussed. Some real-world cases using the integrated techniques will be presented to illustrate the advantages of using proposed methodology.