Flash is supported by a few Verizon phones see (
http://www.adobe.com/aboutadobe/pre...506Verizon.html)
Other than that, flash has yet to be put in phones (in the mainstream, most don't have flash enabled phones.)
The fileformat as far as I have tested does not greatly affect phone usage (a .php will process just like any other would)
I find that XHTML is more compatiable with Mobiles because of the development that phones are XML/WAP so XML HTML works best. If you are not developing in HTML.
- Steve