It is configurable via the Form Options (Browser Category). However I believe it only allows you to show/hide the toolbars. If you want to customize this UI, your best bet is to probably host the InfoPath XmlFormView control in a custom ASPX page. This is a very advanced topic, however, and I will not be able to provide an example (but you could look it up on MSDN if you're willing to go through the trouble).
David Airapetyan / Software Services ArchitectQdabra® Software / Streamline data gathering to turn process into knowledge