How don't save a specific cookie when i call jquery.ajax!!!

Question

Hi, here is my call:

    jQuery.ajax({
         type: "POST",
         url: "http://localhost:8080/axis2/services/AutheticationWS/signin",
            data:{
                    username: myusername, 
                    password: mypassword,
                    platform: myplatform
            },
            dataType: (jQuery.browser.msie) ? "text" : "xml",
            success: function(data,textStatus,XMLHttpRequest) {

                var xml = data;
                //checking if the browser is Internet Explorer
                if (typeof data == "string") {
                    xml = new ActiveXObject("Microsoft.XMLDOM");
                    xml.async = false;
                    xml.loadXML(data);
               }else {
                    xml = data;
               }

               alert("Response Headers: "+XMLHttpRequest.getAllResponseHeaders());

     }

    });

And i take from this call back a idsession from the respone header of the XHR, but is stored in the coοkies of the firefox, and i don't to make this happened!!! And i don't know how to stop!

Thanks for your attention and your time!!