HTML and CSS Reference
used to create fast interactivity without having to wait for a response from the server. As
shown in our Web cycle example in Figure 1.2, the browser sends a request to the server
and waits for a response, often with a little wheel-shaped icon circling around in the
location bar reminding you that the page is loading. As you wait, the browser sits with
you and waits, and after each subsequent request, you must wait for the entire page to
reload to get the contents of the new page. Ajax lets you send data back and forth
between the browser and server without waiting for the whole page to reload. Only parts
of the page that change are replaced. Several requests can go out while you are scrolling,
zooming in and out, filling out a form, and so on, as those other parts are loaded in the
background. Because this interactivity is asnychronous, feedback is immediate with no
long waiting times between requests. Some examples of Ajax applications are Ajax Stock
Qutos Ticker (SentoSoft LTD), Flickr for photo storage and display, Gmail, Google Sug-
gest, and perhaps the best example, Google Maps at maps.google.com (see Figure 1.3).
Figure 1.3 Google uses Ajax for interactivity. © 2010 Google.