user login

[msz]

Dear Friend's!

i have a problem in my user login page.

the problem is that when user login and i click the next page or link, then it will disappear, and when i back to the perivous page then it will not show the user?

what can i do,,,,

my login code is ..

<?php

include './header.php';

include 'connection.php';

if(isset($_POST) && count($_POST)>0) {

$user = $_POST['username'];

$pass = $_POST['password'];



$sSQL = "SELECT * FROM ulog WHERE User_Name ='$user' AND Password = '$pass'";



$result = mysql_query($sSQL) or die(mysql_error());



if(mysql_affected_rows() > 0) {

$row = mysql_fetch_object($result);



$_SESSION['username'] = $row->User_Name;

$_SESSION['password'] = $row->id;

echo "<h4 id='welcome'>welcome &nbsp<a href='#'> $user</a></h4>";



}



else

{

header("location:signup.html");

}

}



?>