Undoubtedly, XMLHttpRequest is the most important function in Ajax. With this function, developers could easily transfer XML files from the client to server. XMLHttpRequest can single-handedly transform your application from a simple website to an Ajax based website. Its asynchronous function makes Ajax one of the coolest website and application technique today. Unfortunately, some developers have used it rather more than they should. Of course when a good thing is overused, it becomes really bad. The case of XMLHttpRequest is no different. When the function is overused it tends to overlap over some of the important things a website should have.