I have a (javascript) web app that offers the user the option to upload a local file which will then be processed by the app. This is not central to the app's function, but it is an important option. Obviously, if the user runs the app on the iPhone, this option will not work (and in fact the app hangs if the iPhone user tries to invoke it). So, what I need is some way to disable this option when the app is being run on the iPhone. Any ideas?