8.14. Finally, The Back Button
The GWT provides a way to restore the functionality of the web browser's back button in an Ajax application. Typically, the state of a single-page Ajax application is not related to the browser's back button.
In other words, the user changes something in the Ajax application by, say, clicking a button or making a selection-list choice, and he cannot go back to the application's previous state by clicking the browser back button. All he can do is reload the web page and thereby restore the page's initial state.
This is because the Ajax application's state is not associated with a URL in the browser's history list, as it is with conventional web browsing. In the conventional manner, if you surf from the New York Times home page to another web page, for example, the back button will bring the user back to the newspaper's home page. This is not true with the various states of an Ajax application, unless you use GWT's mechanism, which this shortcut introduces for you.