In this 4 part series, we talk about how the XMLHttpRequest works. I basically cover the whole aspect of it in depth. Naturally you should and could use the jQuery ajax functions, as they are for sure easier and more reliable, although if done properly the xmlhttprequest can do as much as the jquery library if implemented properly. I talk about the different ready states which the request goes through. The order in which the events are fired, and which header data you need to send back to the server in order to have the post variables available.