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Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at Z:\home\test1.ru\www\reg.php:1) in Z:\home\test1.ru\www\reg.php on line 2
reg.php
<?
session_start();
include_once('system/db.php');
echo'<div class="wa-nav-pos">
<div class="logo"><a href="/"><img src="/img/logo_80975_logo.png" alt="logo" class="img-responsive"></a></div></div>';
echo'<div class="wa-left-block"><div class="title">Меню</div>
<div class="forlink"><a href="/reg.php" class="links"><img src="/img/reg.png" alt="reg">Зарегистрироваться</a></div>
<div class="forlink"><a href="/login.php" class="links"><img src="/img/quest.png" alt="login">Войти</a></div>

</div>';
echo'<div class="wa-center-block"><div class="title">Регистрация</div>';
echo'<div class="menu">';

if (empty($_POST['code'])) {
echo'Введите код с картинки!<br/>';
}
elseif ($_SESSION['code'] != $_POST['code']) {
echo'Код с картинки введен неверно!<br/>';
echo'ses:'; echo $_SESSION['code'];
echo'post:';echo $_POST['code'];
} else {
}
echo'</div>';
echo'<div class="menu"><form name="registration" action="/reg.php" method="POST" >
Логин:<br><input type="text" name="login"><br>
Пароль:<br><input type="password" name="pass"><br>
Повторите пароль:<br><input type="password" name="last_pass"><br>
E-mail:<br><input type="email" name="email"><br>
Имя:<br><input type="text" name="name"><br>
Пол:<br><select name="pol"><option value="1">Мужской</option><option value="2">Женский</option></select><br>
Код с картинки:<img id="captcha" src="/img/code.php" alt="check" onclick="UpCaptcha()"><br><input type="text" name="code"><br><input type="submit" name="reg" value="Зарегистрироваться"><form></div>
</div><div class="ze">
<br>Doubler<span id="li"></span>
<span style="display: none"></span>
</div>';

?>
code.php:
<?php

session_name('SID') . session_start();

$code = rand(11111, 99999);

$_SESSION['code'] = $code;

header('Content-type: image/png');

$img = imagecreate(70, 30);
imagecolorallocate($img, 255, 255, 255);

$x = 0;

for ($i = 0; $i < 5; $i++) {

$x += 10;
$y = mt_rand(4, 8);

$char = substr($code, $i, 1);

$color = imagecolorallocatealpha($img, mt_rand(50, 210), mt_rand(50, 210), mt_rand(50, 210), mt_rand(10, 30));

imagestring($img, 5, $x, $y, $char, $color);

}

imagepng($img);
imagedestroy($img);

?>

А что с ней не так ?

Error_404, ошибку я скинул