Ajax :Disadvantages

* Dynamically shaped pages do not register themselves with the browser's history engine, so clicking the browser's "back" button would not return the user to a previous state of the Ajax-enabled page, but would instead return them to the last page visit before it. Workarounds include the use of unseen IFrames to trigger change in the browser's history and varying the anchor bit of the URL when AJAX is run and monitoring it for change.

* Dynamic web page update also makes it hard for a user to bookmark a particular state of the application. Solutions to this problem exist, many of which use the URL fragment identifier to keep track of, and allow users to return to, the request in a given state.

* Because most web crawlers do not carry out JavaScript code, web applications should give an alternative means of accessing the happy that would normally be retrieve with Ajax, to allow search engines to index it.

* Any user whose browser does not hold Ajax or JavaScript, or simply has JavaScript disable, will not be able to use its functionality. Similarly, devices such as mobile phones, PDAs, and screen readers may not have hold for JavaScript or the XMLHttpRequest object. Also, screen readers that are clever to use Ajax may still not be able to properly read the dynamically generate content.

* The same origin policy prevents Ajax from being used across domains, although the W3C has a draft that would allow this functionality.

* The lack of a standards body behind Ajax income there is no widely adopted best do to test Ajax applications. Testing gear for Ajax often do not appreciate Ajax event models, data models, and protocols.