How to use theme on button. How to apply css to command button.

first sol. is use skin but we have to create different skin for different button. Another sol is use css, keep in mind that set border width to 0px, and height and width to the button. Now the theme is ok but one more thing is which button should press on enter key for the same set submit button use SubmitBehavior property to true and set to false for other button.
1. show button press effect.
2. Press Enter Key will submit the page