In this chapter I described the Microsoft AJAX Library and its main namespaces and objects. By now, you should be familiar with the AJAX library and where to find classes and functionality within it. You should be familiar with the debugging support provided by Sys.Debug. Most importantly, I covered the functionality of Sys.UI.DomElement and Sys.UI.DomEvent, which are used to add functionality to a browser application. Building on this foundation, we’ll look at application services using the Sys.Services application service layer from the Microsoft AJAX Library in the next chapter before moving on to building components and controls.