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
Try appending a unique GET tag to the ends of any and all href attributes, for example:
This would generate href="/css/global.css?########"
, with a different number nearly every time. This forces iOS' Safari to pull the "new" page down, as there is no data in its cache originating from the same URI, and there likely never will be (unless you plan on reloading the app millions of times during development :D )