SelectedIndex – : This property is used for initial display AccordionPane 0 for first 1 for second and 2 for third and..
HeaderCssClass – : This property is used for applying display all AccordionPane Header Style.
HeaderSelectedCssClass- : This property is used for applying display selected AccordionPane Header Style.
ContentCssClass - :This property is used for applying display AccordionPane Content Style.