Custom Button is server-side only?

Custom Button is server-side only?

Is it true that a custom button is server-side only?
I have a use case where I need to clear the selections in a checkbox
picklist on a stateless HTML form. This form does not refresh and cannot
refresh for other reasons so I need to be able to control all of the
form UI elements client side.

How do I clear the selections in a checkbox picklist on the client?
Can the deselectall() be placed in some other clientside object that I
can invoke it's script via the custom button? I don't know, just trying to get this to work.



tt