проверка правильно ли залогиниться юзер
<?php
require_once('header.php');
require_once ('bd.php');

if(isset($_POST['submit']))
{
if (empty($_POST['loginname']) && empty($_POST['password']))
{
echo "error empty login and password";
}
if (empty($_POST['loginname']))
{
echo "error empty login";
}
if (empty($_POST['password']))
{
echo "error empty password";
}


$result = mysql_query("SELECT `password`, `login` FROM `reg_users` WHERE `login`=$form_login, `password`=$form_password");
if ($form_login !== $myrow['login'] or $form_password !== $myrow['password'])
{
echo "login or password dont match";
}
header("index.php");
}


?>

Вот как нужно оформлять код!!!

<?php
require_once('header.php');
require_once ('bd.php');

if(isset($_POST['submit']))
 {
 if (empty($_POST['loginname']) && empty($_POST['password']))
 {
 echo "error empty login and password";
 }
 if (empty($_POST['loginname']))
 {
 echo "error empty login";
 }
 if (empty($_POST['password']))
 {
 echo "error empty password";
 }


 $result = mysql_query("SELECT `password`, `login` FROM `reg_users` WHERE `login`=$form_login, `password`=$form_password");
 if ($form_login !== $myrow['login'] or $form_password !== $myrow['password'])
 {
 echo "login or password dont match";
 }
 header("index.php");
 }


?>