Something

function see_msg()
{
        var xmlhttp = init_xmlhttp();

        if(xmlhttp) {
                xmlhttp.open("GET", "/rpc/rpc_msg.php",true);

                xmlhttp.onreadystatechange = function() {
                        if (xmlhttp.readyState == 4) {
                                if(xmlhttp.responseText != '') {
                                        alert(xmlhttp.responseText);
                                }
                        }
                }

                xmlhttp.send(null);
        }
}

window.onload = startList;
window.setInterval('see_msg()', 10000);