Whether you post to a servlet, cgi,
JSP, or just plain old HTML page, you are going to get a response.
Eric's suggestion of an invisible frame or iframe into which the response can be displayed unseen is your best bet.
(Btw, this is a GREAT technique for making changes to a page via a server round trip without having to refresh the page. The reponse is displayed in an invisible iframe and JavaScript within that response can manipulate the displayed page without a refresh.)
hth,
bear