While the use of Ajax generally makes websurfing more enjoyable for the user, the programmer must be careful not to break accepted website behavior with Ajax. A common problem with Ajax applications is the disability of the web browser's Back button. In a normal non-Ajax application, every webpage has a unique URL. Thus, a user can hit the Back button to take him back to the previous URL, which would be the state that the browser was in before the user's last action. This can be seen as a sort of Undo operation. However, with Ajax the URL of the webpage does not change every time the state of the web application changes. Therefore a press of the back button will bring the user to a state much further back than he might have intended. Also, page bookmarking is dependant upon the URL of the page in question. Therefore, pages created by Ajax will not be bookmarkable. Professional programmers have in fact developed techniques to circumvent these issues, however, they are far from perfect.
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