Maybe someone had encountered such a problem already - despite the fact, that OAuth http://developer.yahoo.com/oauth/ is described as ready for use with mobile phones out-of-the-box it does not appear as such.
I have tried to implement sample application and use Yahoo! PHP SDK to connect with Yahoo! Using web browser it is all nice and easy. But while visiting Yahoo! request_auth page (http://developer.yahoo.com/oauth/guide/oauth-userauth.html) on my test mobile phone (Nokia 6300) it renders unacceptable: I am not able to see login box, cannot read information why my login would be required and all. I just see a page border and some text fragments ("Yahoo!", "Hel" (like in help...) et. al.).