login system - vil kun gå tilbage

HTML kode 

 <form id="loginForm" action="login_godkendt.php" method="post">
             <fieldset id="body">
                 <fieldset>
                     <label for="email">Email Address</label>
                     <input type="text" name="email" id="email" />
                 </fieldset>
                 <fieldset>
                     <label for="password">Adgangskode</label>
                     <input type="password" name="password" id="password" />
                 </fieldset>
                 <input type="submit" id="login" value="Log ind" />
             </fieldset>
             <span><a href="./">Luk ned</a></span>
         </form>

PHP kode 

 <?php
  session_start();
  
  include("include/database/db.php");
 
  $email = $_POST["email"];
  $password = $_POST["password"];
  $error = "";
  
  $userQuery = mysql_query("SELECT id,email,password FROM brugere WHERE email='$email'");
  
  if(mysql_num_rows($userQuery) != 1)
  {
      $error .= "Brugeren eksisterer ikke.<br>";
  }
  else
  {
      $userArray = mysql_fetch_array($userQuery);
  
      if($userArray["password"] != SHA1($pass))
      {
          $error .= "Password og brugernavn passer ikke sammen.<br>";
      }
  }
  if($error != "")
  {
      echo $error . "<a href=\"javascript:history.back(-1);\">Tilbage</a>";
  }
  else
  {
      $_SESSION["logged_in"] = 1;
      $_SESSION["user_id"] = $userArray["id"];
      header("Location: user.php");
  }
  ?>

SQL kode 

 CREATE TABLE IF NOT EXISTS `brugere` (
   `id` int(11) NOT NULL AUTO_INCREMENT,
   `email` varchar(255) DEFAULT NULL,
   `password` varchar(255) NOT NULL,
   `facebook` varchar(255) NOT NULL,
   `land` varchar(255) NOT NULL,
   `profiltekst` text NOT NULL,
   `djnavn` varchar(255) DEFAULT NULL,
   `site` varchar(255) NOT NULL,
   `fk_musik_info` int(11) NOT NULL,
   `profilbillede` varchar(255) NOT NULL,
   `soundcloud` varchar(255) NOT NULL,
   `club` varchar(255) NOT NULL,
   `booking` varchar(255) NOT NULL,
   `pris` int(11) NOT NULL,
   PRIMARY KEY (`id`)
 ) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ;
 
 --
 -- Data dump for tabellen `brugere`
 --
 
 INSERT INTO `brugere` (`id`, `email`, `password`, `facebook`, `land`, `profiltekst`, `djnavn`, `site`, `fk_musik_info`, `profilbillede`, `soundcloud`, `club`, `booking`, `pris`) VALUES
 (1, 'Resource id #23', '7b52009b64fd0a2a49e6d8a939753077792b0554', 'hehej', 'hej', '<p>hejej</p>', 'hehej', '', 1, '4.png', '', 'hejher', 'herjehj', 124124);