Line 13: If we wanted to transmit some data to and from a server we would specify the data to be transmitted. But since we don't want to send data we set the send argument to null

Line 14: A break statement closes the case.

That is the core of an xml asynchronous loading technique. And it is well worth the effort to get to know it intimately. If you don't understand it, try reading it again until you do. The next case is used to signify what is going to happen when the document loads.

Line 15: Creates a new case called start_up.

Line 16: This statement tells the browser what to do when the original document (not the document being loaded into the interface what to do. Here we specify that the ajaxManager function should be called, then to use the case load page, then to retrieve the xml file named