Controls on Web Page shoul not lose their value

Dear Friends,
i have some date,TextBox,Dropdownlist controls on web Form.
Dropdownlist is having AutoPostBack property to True, by which whenever i fill all other Textbox and date details in that Form the controls do not retain their enterd Values and gets Refreshed by which i have to again Enter the Details,
which makes it very uneasy!!!!

Pl reply!!!!

Regards,
aamir