function check_sub(){
  id_document="reg";
  mr_1=document.getElementById('sub_mr_89').value;
request.open('POST', 'includes/check_sub.php',true);
request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded'); 
request.onreadystatechange = parseInfo; 
request.send('sub=' + mr_1);
}