[ Thanks to IdaAshley for this link.
]
“A major challenge of Asynchronous JavaScript and XML
(Ajax)-driven Web sites is the lack of a Back button. We will use
JavaScript to create a history stack for the Ajax photo gallery
built in Part 1 of this two-part ‘Developing PHP the Ajax way’
series. This history stack will closely mirror the history utility
found in Web browsers, and it will be used to provide Back,
Forward, and Reload buttons for the application…”