Boa tarde, alguém conhece este erro, ja tentei diversas formas mas não consigo corrigir, estou criando o coontrole de login.
****************arquivo do login index.html***********************
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="">
<meta name="author" content="">
<link rel="shortcut icon" href="../../docs-assets/ico/favicon.png">
<title>Login Pabx Management</title>
<!-- Bootstrap core CSS -->
<link href="css/bootstrap.css" rel="stylesheet">
<!-- Custom styles for this template -->
<link href="css/signin.css" rel="stylesheet">
<!-- Just for debugging purposes. Don't actually copy this line! -->
<!--[if lt IE 9]><script src="../../docs-assets/js/ie8-responsive-file-warning.js"></script><![endif]-->
<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->
</head>
<body>
<div class="container">
<form class="form-signin" role="form" method ="post" action="sessao.php">
<h2 class="form-signin-heading">Fazer o Login</h2>
<input type="text" class="form-control" name="login" placeholder="Login" required autofocus>
<input type="password" class="form-control" name="senha" placeholder="Senha" required>
<label class="checkbox">
<input type="checkbox" value="remember-me"> Lembrar Minha Conta
</label>
<button class="btn btn-lg btn-primary btn-block" type="submit">Login</button>
</form>
</div> <!-- /container -->
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
</body>
</html>
*************Este é o arquivo sessão php que recebe os dados do login sessao.php**************************
<?php
session_start();
$login = $_POST['login'];
$senha = $_POST['senha'];
include_once("conexao.php");
$sql = mysql_query("SELECT * FROM clientes WHERE login = '$login' and senha = '$senha'") or die(mysql_error()) ;
$row = mysql_num_rows($sql);
if($row > 0 )
{
$_SESSION['login'] = $login;
$_SESSION['senha'] = $senha;
echo "Login Efetuado com sucesso";
header('location:main.php');
} else
{
unset ($_SESSION['login']);
unset ($_SESSION['senha']);
header('location:index.html'); }
?>
*****Essa é a página principal para onde dever redirecionada após o login main.php**************
<!DOCTYPE html>
<html lang="en">
<head>
<?php
/* esse bloco de código em php verifica se existe a sessão, pois o usuário pode simplesmente não fazer o login e digitar na barra de endereço do seu navegador o caminho para a página principal do site (sistema), burlando assim a obrigação de fazer um login, com isso se ele não estiver feito o login não será criado a session, então ao verificar que a session não existe a página redireciona o mesmo para a index.php. */
if((!isset ($_SESSION['login']) == true) and (!isset ($_SESSION['senha']) == true))
{
unset($_SESSION['login']);
unset($_SESSION['senha']);
header('location:index.php');
}
$logado = $_SESSION['login'];
?>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="">
<meta name="author" content="">
<link rel="shortcut icon" href="../../docs-assets/ico/favicon.png">
<title>PABX Management</title>
<!-- Bootstrap core CSS -->
<link href="css/bootstrap.css" rel="stylesheet">
<!-- Custom styles for this template -->
<link href="css/navbar.css" rel="stylesheet">
<!-- Just for debugging purposes. Don't actually copy this line! -->
<!--[if lt IE 9]><script src="../../docs-assets/js/ie8-responsive-file-warning.js"></script><![endif]-->
<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->
</head>
<body>
<?php
echo" Bem vindo $logado";
?>
<div class="container">
<!-- Static navbar -->
<div class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">PABX Management</a>
</div>
<div class="navbar-collapse collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="formulario.php">Cadastro de Usuários</a></li>
<li><a href="#">Cadastro de Clientes</a></li>
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">Listar Clientes <b class="caret"></b></a>
<ul class="dropdown-menu">
<li><a href="#">Pesquisar</a></li>
<li><a href="#">Editar Dados</a></li>
<li><a href="#">Excluir</a></li>
<li class="divider"></li>
<li class="dropdown-header">#$%#$%&</li>
<li><a href="#">#$%#$%&</a></li>
<li><a href="#">#$%#$%&</a></li>
</ul>
</li>
</ul>
<ul class="nav navbar-nav navbar-right">
<li class="active"><a href="./">Download</a></li>
<li><a href="../navbar-static-top/">Upload</a></li>
<li><a href="../navbar-fixed-top/">Logout</a></li>
</ul>
</div><!--/.nav-collapse -->
</div>
<!-- Main component for a primary marketing message or call to action -->
<div class="jumbotron">
<h1>Software Pabx Management</h1>
<p>
<a class="btn btn-lg btn-primary" href="../../components/#navbar" role="button">View navbar docs »</a>
</p>
</div>
</div> <!-- /container -->
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="https://code.jquery.com/jquery-1.10.2.min.js"></script>
<script src="js/bootstrap.min.js"></script>
</body>
</html>