function getEvent(event) {
 return (event ? event : window.event);
}

function handleKeyPress(event) {
  e = getEvent(event);
  kc = e["keyCode"];
    if (kc == 13) {
        document.forms[0].submit();
    }
}

if (document.addEventListener) { 
    document.forms[0].elements['g_password'].addEventListener("keyup", handleKeyPress, false);
} else {
    document.forms[0].elements['g_password'].onkeyup = handleKeyPress;   
}