Where to place script for link

I’m building a social network website and I was doing so well until now. ALL my connections are good. I’ve got my script in the proper file / location. When I click on the link to go back to the sign in page, I get this error.

This is my error response…

The webpage cannot be found

HTTP 404

Most likely causes:

There might be a typing error in the address.

If you clicked on a link, it may be out of date.

Having a difficult time where to place the link to my sign in page.

This is my script…

<?php

// Start_session, check if user is logged in or not, and connect to the database all in one included file

include_once("scripts/checkuserlog.php");

?>

<?php

if (!isset($_SESSION['idx'])) {

echo '<br /><br /><font color="#FF0000">Your session has timed out</font>

<p><a href="pm_sentbox.php.php">Please Click Here</a></p>';

exit();

}

// Decode the Session IDX variable and extract the user's ID from it

$decryptedID = base64_decode($_SESSION['idx']);

$id_array = explode("p3h9xfn8sq03hs2234", $decryptedID);

$my_id = $id_array[1];

$my_uname = $_SESSION['username']; // Put user's first name into a local variable

// ------- ESTABLISH THE INTERACTION TOKEN ---------

$thisRandNum = rand(9999999999999,999999999999999999);

$_SESSION['wipit'] = base64_encode($thisRandNum); // Will always overwrite itself each time this script runs

// ------- END ESTABLISH THE INTERACTION TOKEN ---------

?>

<?php

// Mailbox Parsing for deleting inbox messages

if (isset($_POST['deleteBtn'])) {

foreach ($_POST as $key => $value) {

$value = urlencode(stripslashes($value));

if ($key != "deleteBtn") {

$sql = mysql_query("UPDATE private_messages SET senderDelete='1' WHERE id='$value' AND from_id='$my_id' LIMIT 1");

// Check to see if sender also removed from sent box, then it is safe to remove completely from system

}

}

header("location: pm_sentbox.php");

}

?>

Please Help!

Thanks in advance,

Scotty13