Is there a way to CSS style an InfoPath 2007 form rendered by Forms Server 2007? It seems to be somewhat of a "black box", but the formatting options in the Infopath client are pretty limited.
Here is a blogpost related to your question.
http://www.infopathdev.com/blogs/greg/archive/2005/06/07/Add-a-Custom-Style-Sheet-to-a-View.aspx