The trickiest part of Ajax development is knowing what is happening in the seemingly black box request. Even if we define what data and URL we are using to make the request, if something happens that we have not accounted for in our coding, we may never know what was returned from the server.
Let us ready ourselves for this chapter by having one of the best tools to debug Ajax requests. We make ourselves familiar with Firefox Firebug, firstly, by downloading the Firefox browser from http://firefox.com. Once that is installed, we choose Tools from the horizontal menu, and then select Add-ons from the resulting drop-down menu. Finding and installing the Firebug add-on is simple; just search for Firebug and follow the directions to install it and restart Firefox. Once it is installed a tiny firebug icon will be evident in the status bar: