PHP - Error al enviar los datos a mi base de datos con php

<?php

$host="localhost"; // Host name 

$username="root"; // Mysql username 

$password=""; // Mysql password 

$db_name="bd1"; // Database name 

$tbl_name="usuarios"; // Table name 

// Connect to server and select database.

mysql_connect("$host", "$username", "$password")or die("cannot connect");

mysql_select_db("$db_name")or die("cannot select DB");

// Get values from form 

$name= isset($_POST['name']) ? $_POST['name'] : null ;

$lastname= isset($_POST['lname']) ? $_POST['lname'] : null ;

$email= isset($_POST['mail']) ? $_POST['mail'] : null ;

$password= isset($_POST['pass']) ? $_POST['pass'] : null ;

// Insert data into mysql 

$sql="INSERT INTO $tbl_name(Nombre, Apellido, Correo, Contraseña)VALUES('$name', '$lastname', '$email', '$password')";

$result=mysql_query($sql);

if($result){

echo "Successful";

echo "<br>";

echo "<a href='tuimport.html'>Back to main page</a>";

}

else {

echo "ERROR";

}

?>

echo ('error query: ' . mysql_error());