I have the same error message when i put any error in the file

when I submit this form i have the same error message all the time . even if i put right or wrong password or don't put password or i write the name of the data base wrong . all of this wrongs i have the same error message : Please enter a username and password . so what is the problem . and i am sure about my fields on data base .

    <?

    session_start();
    $username = $_POST['username'];
    $password = $_POST['password'];


    if ($username && $password)
    {

        $connect = mysql_connect("localhsost","root","adminffpass") or die("Couldent connet to database ");
        mysql_select_db("login") or die("No data base found ");

        $query = mysql_query("SELECT * FROM users WHERE username='$username'");

        $numrows = mysql_num_rows($query);

        if ($numrows !=0)
        {

            while ($row= mysql_fetch_array($query)) 
            {

                $dbusername = $row['username'];
                $dbpassword = $row['password'];

            }

            if ($username == $dbusername && $password==$dbpassword)
            {
                echo "Login successul .<a href='memeberarea.php'>Click to enter member area</a>";
                $_SESSION['username'] = $dbusername;
            }
            else
                echo "incorrect  password  ";

        }
        else
           die ("That user name dosent exist");

   }
   else
     die ("Please enter a username and password");


    ?>