I want not to reload the page when Dropdown chage is done+asp.net

[Chetana]

Hi All,
I have one asp.net site and my page gets refershed on selection of
dropdowns from that page.
I want not to refersh the page .how i will do this. and i have made
autopostback=tr ue
because i want selected chage og that dropdown and for validation also
i want that evemt to be true.
Also i donot want to use ajax.
If anyone has any idea reply me immidiately.

Thanks