The course presents the principles that guide the Web and make it so successful. We begin with an introduction of the historical issues and the first attempts at similar systems. Then we detail the architecture of the web, including the multiple complementary standards and their roles in the big picture, but also including important proprietary back-end technologies like ASP. The students learn good practices for web engineering, important mainly for accessibility and scalability of web applications. Finally, the course introduces the topic of distributed applications on the web, with special focus on design issues and applicability of Web Services technologies.