會話沒有通過

我有一個account.php頁面，用戶可以更改保存在mySQL數據庫上的帳戶信息。當我點擊鏈接時，我會收到一條消息，說「在訪問此頁之前回去登錄！」我的代碼如下。會話沒有通過

pro.php（涉及一次登錄頁）在pro.php頁面頂部

<?php 

//STEP 1 Connect To Database 
$connect = mysql_connect("Localhost","mlec2013_danny","8764963d"); 
if (!$connect) 
{ 
die("MySQL could not connect!"); 
} 

$DB = mysql_select_db('mlec2013_database'); 

if(!$DB) 
{ 
die("MySQL could not select Database!"); 
} 

//STEP 2 Declare Variables 

$Name = $_POST['username']; 
$Pass = $_POST['password']; 
$Query = mysql_query("SELECT * FROM Users WHERE Username='$Name' AND Password='$Pass'"); 
$NumRows = mysql_num_rows($Query); 
$_SESSION['username'] = $Name; 
$_SESSION['password'] = $Pass; 

//STEP 3 Check to See If User Entered All Of The Information 

if(empty($_SESSION['username']) || empty($_SESSION['password'])) 
{ 
die("Go back and login before you visit this page!"); 
} 

if($Name && $Pass == "") 
{ 
die("Please enter in a name and password!"); 
} 

if($Name == "") 
{ 
die("Please enter your name!" . "</br>"); 
} 

if($Pass == "") 
{ 
die("Please enter a password!"); 
echo "</br>"; 
} 

//STEP 4 Check Username And Password With The MySQL Database 

if($NumRows != 0) 
{ 
while($Row = mysql_fetch_assoc($Query)) 
{ 
$Database_Name = $Row['username']; 
$Database_Pass = $Row['password']; 
} 
} 
else 
{ 
die("Incorrect Username or Password!"); 
} 


//end of PHP scripting. Information displayed below is in the form of HTML, CSS, or Javascript. 
?>

account.php