[help] why wont this work?

<?php 
session_start(); 
include "config.php"; 
if($logged[username] && $logged[userlevel] == 6) 
{ 
switch($_GET[action]) 
{ 
default: 
$fetch = mysql_query("SELECT * FROM `members`"); 
while ($delete = mysql_fetch_array($fetch)) 
{ 
echo ("- <a href='?page=delete/user&action=verifydelete&username=$delete[username]'>$delete[username]</a><br>"); 
} 
break; 
 
case 'verifydelete': 
echo ("Are you sure you want to delete $_GET[username]? 
<br><br> 
<a href='?page=delete&username=$_GET[username]'>Yes</a> - <a href='delete_user.php'>No</a>"); 
break; 
 
case 'delete': 
$username = strip_tags(htmlspecialchars($_GET[username])); 
$delete = mysql_query("DELETE FROM `members` WHERE username = '$username'"); 
echo ("User Deleted.<br><a href='delete_user.php'>Go back.</a>"); 
break; 
} 
} 
else 
{ 
echo ("You must be admin to view this page."); 
} 
?>