Untitled

<?php
session_start();
include_once ('config.php');

ob_start();

if(isset($_POST['submit']) && !empty($_POST['username']) && !empty($_POST['password'])) {

$username = $_POST['username'];
$password = $_POST['password'];
$username = mysql_real_escape_string($username);
$password = md5($password);
$sql = mysql_query("SELECT * FROM users WHERE username = '$username' AND password = '$password'");
$nr = mysql_num_rows($sql);
if($nr == 0) {
echo '<div class="errormsg">Username or Password is incorrect</div>';
}else{
while($row = mysql_fetch_array($sql)) {
$_SESSION['lia'] = $row['username'];
}
header ('Location: me.php');
}
}
ob_flush();
?>
<html>
<head>
<link href='/login.css' rel='stylesheet' type='text/css'>
<title>Welcome ZeloCMS</title>
</head>
<body>
<div class="loginBox">
<div class="mid">
<center><a href='register.html'><div class=register_box>Register Today!</div></a></center>
<center><form action='index.php' method='POST'>
<b>Username: <input type='text' name='username'><br />
<b>Password: <input type='password' name='password'><br />
<input type='submit' name='submit' value='Sign In' " />
</form></center></div></div>
</body>
</html>