?? Warning: session_start() [function.session-start]: Cannot send session cookie กรุณาเข้ามาอ่านก่อนครับ

<?
session_start();
if($_SESSION['username'] == '') { require_once("login.php"); }
if($_SESSION['username'] != '') {
	require_once("function/func_connect.php");
		if($_GET[action] == 'logout') {
  
  	session_destroy();
	/*session_unset($_SESSION["id"]);
	session_unset($_SESSION["username"]);
	session_unset($_SESSION["password"]);
	session_unset($_SESSION["status"]);
	session_unset($_SESSION["money"]);*/
  echo '<META HTTP-EQUIV="Refresh" CONTENT="0;URL=index.php">';
  
  
  }
?>

<?
session_start();
	require_once("function/func_connect.php");
if(isset($_SESSION["id"]))
{
	header("location:index.php");
}
if($_SESSION["id"] != "")
{
	header("location:index.php");
}
?>