Web applications changed a lot in the last decade. The starting point was a simple static page, written in HTML, to show texts and images. A fast evolution brought us to dynamically generated pages (through CGI or server side scripting languages) that permits to create personalized content for user's needs, and so, the creation of e-commerce applications and so on.

The problems arised in these cases are linked to the too simple interface that a web page can offer, that makes simple desktop-like operations a far mirage for on-line web applications. Moreover the user interaction with the web application is a simple click-wait-reload action, that causes long waiting periods. Some tries were made during the years to solve this problems, the more of them uses browsers' plugins that need to be downloaded and added to the browser in order to make possible some enhancements in the interface. This solution has a big problem, for a strange reason, when a user tries to use a web site that envelop an object handled by one of this plugins, his browser fires one of the next possible advices:

• You don't have a plugin to run the page's content

• Your plugin is not up-to-date, please download the last version

The strange is in the fact that these advices appear more frequently than expected. The reality is quite simple, user downloads one time the plugin, but developers use, during months, different versions of that plugins for their applications, this makes the user's version not good. For expert users this is not a big problem, but for the others this could bring to not use that web site.

This work presents solutions to avoid these problems and techniques to bring a new evolution in web development, following a trend already started with the great work of some organizations, like Google, that makes applications (software) much more similar to services than to products.

This work is organized in 5 chapters:

• Chapter I: A brief introduction to the web technologies evolution and on the future trends and research topics;

• Chapter II: The description of the technology that has revolutionized the web development, AJAX, and of linked issues;

• Chapter III: In this chapter are presented some of the most known security threats for web applications and their possible solutions;

• Chapter IV: To provide complex web applications there is the need for an RPC framework, here are analyzed the requirements for such framework and possible implementations;

• Chapter V: For sample purpose, here is presented a simple chat application realized through the presented technologies.