It would appear that Apple have changed the way homescreen/standalone web apps work in iOS 6. According to various blog posts (example) these apps now get their own dedicated s
This drove me nuts for a while. Tried clearing the cache on device - no luck. Renaming the page did help, but once you rename it back, you still get the same stale version. Found the solution yesterday. You need to connect your device to Mac and open Web Inspector in Safari Develop menu. Once in Web Inspector, simply press "Reload page" button on the Inspector's toolbar and - voila - you see the fresh version on your device's screen.