Because the server returns a new page each time the user submits input, traditional web applications can run slowly and tend to be less user-friendly.
With an HTTP request, a web page can make a request to, and get a response from a web server – without reloading the page. The user will stay on the same page, and he or she will not notice that scripts request pages, or send data to a server in the background.
AJAX was made popular in 2005 by Google (with Google Suggest).
The XMLHttpRequest object is supported in Internet Explorer 5.0+, Safari 1.2, Mozilla 1.0 / Firefox, Opera 8+, and Netscape 7.