The current situation in the development of Web applications is reminiscent of the early days of software systems, when quality was totally dependent on individual skills and lucky choices. In fact, Web applications are typically developed without following a formalized process model: requirements are not captured and design is not considered; developers quickly move to the implementation phase and deliver the application without testing it.

Not differently from more traditional software system, however, the quality of Web applications is a complex, multidimensional attribute that involves several aspects, including correctness, reliability, maintainability, usability, accessibility, performance and conformance to standards.

In this context, aim of this PhD thesis was to investigate, define and apply a variety of conceptual tools, analysis, testing and re-structuring techniques able to support the quality of Web applications. The goal of analysis and testing is to assess the quality of Web applications during their development and evolution; re-structuring aims at improving the quality by suitably changing their structure.