Source: http://developer.apple.com/iphone/designingcontent.html
scroll down to near the bottom
Unsupported Technologies
You’ll want to avoid using Flash and Java for iPhone content. You’ll also want to avoid encouraging users from downloading the latest Flash to their iPhone, because neither Flash nor downloads are supported by Safari on iPhone.
Safari on iPhone does not support:
window.showModalDialog()
- Mouse-over events
- Hover styles
- Tool tips
- Java applets
- Flash
- Plug-in installation
- Custom x.509 certificates