modal.html

<div class="modal fade" id="myModal" role="dialog">
        <div class="modal-dialog">
            <!-- Modal content-->
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal">&times;</button>
                    <h2 class="modal-title">Log in</h2>
                </div>
                <div class="modal-body">
                        <div class="contact-form">
                                  <form method="POST" action="validar.php">
                                      <div>
                                          <span>Usuario</span>
                                          <span><input type="username" class="form-control" name="email" id="email"></span>
                                      </div>
                                      <div>
                                          <span>Contraseña</span>
                                          <span><input type="password" class="form-control" name="clave" id="clave"></span>
                                      </div>
                                            <input type="hidden" name="location" value="index.php">
                                     <div>
                                             <label class="fa-btn btn-1 btn-1e"><input type="submit" name="submit" value="Entrar"></label>
                                             <a href="Registro.php" class="fa-btn btn-1 btn-1e">Registrarse</a>
                                    </div>
                                  </form>
                              </div>
                </div>
            </div>
        </div>    
    </div>
</div>