Ajax, Flash and Flex have brought real interactivity to the internet. The UIs they create are visually richer, and, unlike html, offer great flexibility of interaction design nearly equal to what can be done on the desktop. However, these apps still run within a browser. Many of these new apps, in reaching forward with these new tools, have, unfortunately thrown a bit of the baby out with the bathwater. They break the best thing about web browsers – the dead simple and universally functional navigation scheme of the back and forward button. That means that when you hit the back button, you sometimes end up somewhere at best surprising, but more often, annoying.
This problem can be avoided. The engineers I worked with at Adobe came up with a few tricks to ensure that the boring, but beautiful forward and back buttons still work. Please follow their example. Don’t break the back button.