как мога да направя тази заявка да не е $_SESSION['error'] ами $_GET['error'] ? 
PHP:
<?php
session_start();
require ("config.php");
$username = addslashes($_POST['username']);
$password = md5(addslashes($_POST['password']));
if($_SERVER['REQUEST_METHOD'] != "POST")
{
header('Location: index.php');
}
if(isset($_POST['submit'])) {
if(isset($username) && isset($password))
{
$q = mysql_query("SELECT username, password FROM users WHERE username='$username' AND password='$password' LIMIT 1");
if(mysql_num_rows($q) == 1)
{
$user = mysql_fetch_assoc($q);
$_SESSION['username'] = $user['username'];
header("Location: index.php");
}
else
{
$error = "Грешно име или парола";
$_SESSION['error'] = $error;
?>
<meta http-equiv="refresh" content="0; index.php">
<?
}
}
}
?>
PHP:
<?php if($_SESSION[error]) { ?>
<table class="red" align="center">
<tr>
<td>
<center><b><?php print $error; session_destroy(); ?></b>
</td>
</tr>
</table>
<?php
}
?>