This book is based on the author's Graduation thesis at Pisa, University of Pisa 2010. It is a study and an analysis of the technologies used in the development of a web application, especially architectures and models. The work is not exhaustive but it gives an overview of all the players involved in a web application development. The publication begins with an analysis of the architecture and functionalities of both the the web browser and the web server. Then the book proceeds with a description of the AJAX and REST technologies, which have produced a paradigm shift in web application design. Next, in light of the analyzed technologies, the various web application development approaches have been investigated using an appropriate level of abstraction. Finally, the work ends with a discussion of the state management mechanisms and the event-loop, both on the client-side and on the server-side, which have been the main issue in the research of web application development because of the stateless nature of HTTP protocol.