Is there ANY way to suppress the browser's login prompt on 401 response when using XmlHttpRequest

$.ajax({
            type: "POST",
            url: postUrl + "/SomePageMethod",
            data: "{searchString:"" + escape(searchString) + ""}",
            contentType: "application/json; charset=utf-8",
            beforeSend: function(xhr) {
                xhr.setRequestHeader("X-MicrosoftAjax","Delta=true");
            },
            dataType: "json",
            success: onSuccess,
            error: onError
        });

function onError(xhr, e, textStatus) {
    var isAjaxRedirect = xhr.status == 200 && xhr.responseText.match(/pageRedirect/);
    if (isAjaxRedirect == "pageRedirect") {
        // forms authentication ticket expired
        location.href = "a session timeout page, or a login page or whatever";
    }
}