[jQuery] help please. ajax call get status 0 and responseText null

[tonygale]

here is source code. In my javascript function I use jquery to make a
ajax call. myurl is a jsp in localhost which will output a xml.
However i got status 0(not 200). What happen?
$.ajax({
        type:"POST",
        url:myurl,
        data: params,
        complete:function(XMLHttpRequest,textStatus){
                alert("respons status "+XMLHttpRequest.status+" content:
"+XMLHttpRequest.responseText+" header:
"+XMLHttpRequest.getAllResponseHeaders());

        }

        });

Here is the jsp:
<%response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
String ajaxRs="<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>";
ajaxRs=ajaxRs+"<response>";
ajaxRs=ajaxRs+"<message>test!</message>";
ajaxRs=ajaxRs+"</response>";
                System.out.println(ajaxRs);
                response.getWriter().write(ajaxRs);
%>

backend is websphere+ db2.

Can anybody help me?

Thanks a lots!