There are following situation when u should not be use AJAX.
When you make a SEO friendly website at time AJAX should not be used.
- Page data is dynamic within an AJAX application. Search engine spiders do not load a page and execute its JavaScript. This results in search engines ignoring an application or a page. This can lead to lost visitors, but it will not be an issue for internal intranet applications.
- The Really Simple History (RSH) JavaScript library highlights another major issue with Web applications that use AJAX: There is no browsing history, so Back/Forward buttons become useless.