Google??™s calendar (http://calendar.google.com) also shows good use of
Ajax with the ability to drag and drop calendar events in order to change their date and time.
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Figure 4.1: Google Suggest uses Ajax to provide contextual auto completion
As with any technology, there are advantages and disadvantages to using it. The main advantages are that
the user??™s workflow is interrupted much less as the application feels more responsive, the user interface is
more intuitive and less bandwidth is used as only the required data is sent from the server. The main
disadvantages are that Ajax applications tend to break well-known browser features such as the back button
and reliable URLs on the address bar for bookmarks or emailing to other people. There are also additional user
interface issues for the web designer to be concerned about, such as providing notification of processing as the
???spinning globe??? no longer performs this task. Websites that use Ajax can also have problems with adhering to
the WAI accessibility guidelines, so a fall back system is often required.
4.1.1 Defining Ajax
Ajax came into use in 2005 as a way of describing the suite of technologies used to build dynamic websites
and the official expansion is Asynchronous JavaScript and XML.
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