login problems

JackOfBlades

can any tell me whats wrong with this code? here's my problem...in my login page of course u have to login with your username and password and if you entered them correctly you will be redirected to the home page..but here's my problem if u press back...of course you'll go back to the previous page which is the login page...but if u press forward you cant go back to the home page? how come? my cookie's can only be unset if you logout but how come pressing the forward button wont allow me to go back? heres my code:

<?php

header("Cache-Control: no-store, no-cache, must-revalidate");

		 $userName = $_POST['username'];
		 $password = $_POST['password'];

		 $query = "SELECT *
		           FROM userAccount
				   WHERE userName = '$userName' AND password = '$password'";


	 $flag = $_GET['flag'];

	  if($flag == 1)
	   {
	      setcookie("status","",time()-3600);
		  print_r($_COOKIE); 
		}      

	       include("dbInfo.php");

		 $result = mysql_query($query);
		 $data = mysql_fetch_array($result);

   if($userName != NULL && $password != NULL)
    {
	    if(mysql_num_rows($result) == 1)
		 {
			     if(!isset($_COOKIE['status']))
				    {
				      //$stats = "logged";
				      setcookie("status",$data['schoolID'],time()+3600)
				      or die("could not set cookie");
				    }
			    header('location:home.php');
		}
	}

flag is taken from the navigation button which is <a href = logout?flag=1>

thread_PHP

<?php
session_start();
require_once("lib/properties.php");
require_once("lib/configure.php");	
$ob=new Properties;		  

$ob->openDB();  

$ob->selDB();	
$qry = sprintf("select id,text from textimage");
$res = mysql_query($qry);
$txtimage = array();
while ($row = mysql_fetch_array($res,MYSQL_BOTH))
  {
  	$txtimage[$row['id']] = $row['text'];		

  }
$unam = $txtimage[1];  

$password =  $txtimage[2];
$Login = $txtimage[3];

$Reset = $txtimage[4];
?>
<HTML><HEAD><LINK href="bild_files/mn.css" rel=stylesheet type=text/css>
<META content=TRUE name=MSSmartTagsPreventParsing>
<META content=false http-equiv=imagetoolbar>
<META content="MSHTML 5.00.3813.800" name=GENERATOR>
<script language="JavaScript" type="text/JavaScript">
<!--
function MM_reloadPage(init) {  //reloads the window if Nav4 resized
  if (init==true) with (navigator) {if ((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.MM_pgW=innerWidth; document.MM_pgH=innerHeight; onresize=MM_reloadPage; }}
  else if (innerWidth!=document.MM_pgW || innerHeight!=document.MM_pgH) location.reload();
}
MM_reloadPage(true);
//-->
</script>


<link href="class.css" rel="stylesheet" type="text/css">
<script language='JavaScript'>
function chkfocus()
{
document.customer.txtuser.focus();
}
function chkdetails()
{
if(document.customer.txtuser.value == "")
{
alert("Please enter user name");
document.customer.txtuser.focus();
return false;
}

if(document.customer.txtpassword.value == "")
{
alert("Please enter password");
document.customer.txtpassword.focus();
return false;
}
}
</script>
</HEAD>
<BODY  bgcolor="#6C6C6C"  style='background-repeat:repeat' topmargin="0" leftmargin="0" onload='chkfocus()'>
<br>
<br>

<form name="customer" method="post"  target="_top" action="processLogin.php">
<input type=hidden name=languageid value=1>
<TABLE  border="0" cellPadding="0" cellSpacing="0" width="100%">
  <TBODY>
    <TR> 
      <TD align="left" width="100%" height="120">&nbsp; </TD>
    </TR>
  </TBODY>
</table>
      <TD width="100%" align="center">
	   <TABLE  border=0 cellPadding=2 cellSpacing=1 width=465 align="center">
<TBODY>
            <TR> 
              <TD align="center" valign="middle"> 
<P align="center"><font color="#FFFFFF" size="2" face="Geneva, Arial, Helvetica, sans-serif"><?php echo $txtimage[7];?><strong></strong></font></P></TD>
            </TR>
          </TBODY>
        </TABLE></TD>

<TR> 
  <TD width="100%" align="center">
   <TABLE border=1 borderColor="#000000" cellPadding=0 cellSpacing=0 align="center" style="BORDER-BOTTOM: #000000 1px solid; BORDER-COLLAPSE: collapse; BORDER-LEFT: #000000 1px solid; BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid">
      <TBODY>
        <TR> 
          <TD width="465"> <TABLE border=0 borderColor=#000000 cellPadding=0 cellSpacing=0 
        style="BORDER-COLLAPSE: collapse" width=465>
              <TBODY>
                <TR> 

                  <TD bgColor=#3d4351 width=365> <TABLE border=0 borderColor=#111111 cellPadding=5 
              cellSpacing=0  style="BORDER-COLLAPSE: collapse" 
              width=518>
                  <TBODY>
                    <TR> 
                      <TD width=29><span class="typebody">
					  <FONT color=#000000 face="verdana, Geneva, Arial" size=2>&nbsp;</FONT>
					<FONT color=#ffffff face="verdana, geneva, arial" size=1><?php echo $unam;?></FONT>
					</TD>
                      <TD width=316><INPUT name=txtuser class="textbox"  style="FONT-FAMILY: verdana, geneva, arial; FONT-SIZE: 9pt" maxLength=40></TD>
                    </TR>
                    <TR> 
                      <TD width=29><FONT color=#ffffff face="verdana, geneva, arial" size=1><?php echo $password;?>&nbsp;</FONT></TD>  <!-- password -->
                      <TD width=316><INPUT name=txtpassword type=password class="textbox"  style="FONT-FAMILY: verdana, geneva, arial; FONT-SIZE: 9pt" maxLength=40></TD>
                    </TR>
                    <TR align="center"> 
					<TD align="center">&nbsp;</TD>
                      <TD align="center"><INPUT name="Submit" type=submit class="buttonbg" style="FONT-FAMILY: geneva, arial; FONT-SIZE: 8pt" value="<?php echo $Login; ?>"> 
                        <input  name="Reset" type="reset" class="buttonbg"style="FONT-FAMILY: geneva, arial; FONT-SIZE: 8pt"  value="<?php echo $Reset;?>">
                        <!--submit-->                              <!-- reset -->
                      </TD>

                    </TR>
                  </TBODY>
                </TABLE></TD>
                </TR>
                <TR> 
                  <TD bgColor=#000000 colSpan=2 height=1 width=463><IMG border=0 
              src="Login_files/blackdot.gif"></TD>
                </TR>
                <TR> 
                  <TD bgColor=#3d3d3d colSpan=2 width=463> <TABLE border=0 borderColor=#111111 cellPadding=0 
              cellSpacing=0
              style="BORDER-COLLAPSE: collapse" width="100%">
                      <div align="center"><a href="usrmgmt/user_reg1.php"><font color="#FFFFFF" size="1" face="Verdana, Arial, Helvetica, sans-serif"><?php echo $txtimage[6];?></font></a></div>  <!-- new user registration-->
                    </TABLE></TD>
                </TR>

              </TBODY>
            </TABLE></TD>
        </TR>
      </TBODY>
    </TABLE>
</form>  

</BODY>
</HTML>

<?php
$ob->closeDB();
?>

<?php
require_once("lib/properties.php");
error_reporting(0);

session_start();

$prob=new Properties;
	$prob->openDB();
	$prob->selDB();
	$strusername=$_REQUEST['txtuser'];
$strpassword=$_REQUEST['txtpassword'];
$strqry=sprintf("select * from mgmtusers where userid='%s'",$strusername);

$rs=mysql_query($strqry);
$chkactivestatus=1;
$noofrows=mysql_affected_rows();

	print("<html>");
    print("<head>");
    print("<title>Login Detials</title>");
    print("</head><link href='class.css' type='text/css' rel='stylesheet'>");
    print("<body bgcolor='#fffff0'>");
	print("<form method=post action='index.php'>");
	if($noofrows > 0)
	{
		while($row=mysql_fetch_array($rs,MYSQL_BOTH))
		{
			$userpassword=$row['password'];
			$chkactivestatus=$row['status'];
		}
		if($chkactivestatus==0)
		{
			print("<center><font color=white size=8><br>You are not authorised user to login.");
			print("<br><input type=submit class=buttonbg value=GoBack></font></center>");
			exit;
		}
		if($userpassword==$strpassword)
		{
			$_SESSION['loguid']=$strusername;
			$menuname= $_SESSION['menuname'];
			 print "<script language='javascript'>";
			 print "parent.location.href='index.php'";
			print "</script>";

		}
		else 
		{
				   $strerror="<font color=red><br><h2>Entered Password Wrong.</h2>";
                   $strerror=$strerror."<br>Forgot userID, CALL  0044900 our HOT LINE number for further help";
                   $strerror=$strerror."<br>If you are not registred,Register from NEW USER REGISTRATION.</font>";
                    print "<script language='javascript'>";
					print "window.location.href='loging.php?strerror=$strerror'";

					print "</script>";

		}

	}
	else 
	{
			   $strerror="<font color=red><br><h2>No user found</h2>";
               $strerror=$strerror."<br>Forgot userID, CALL  0044900 our HOT LINE number for further help";
               $strerror=$strerror."<br>If you are not registred,Register from NEW USER REGISTRATION.</font>";
                print "<script language='javascript'>";
				print "window.location.href='loging.php?strerror=$strerror'";
				print "</script>";
	}



$prob->closeDB();
?>
 <?php
class Properties
{

function openDB()
{
	mysql_connect("localhost","root","") or die("Sorry Unable to connect".mysql_error());
}
function selDB($dbnam="oscommerce")
{
	mysql_select_db($dbnam);
}


function closeDB()
{
	mysql_close();
}
			?>
<?php
/*
  $Id: configure.php
  */
  define('READ', '30'); // for read permission to the page.
   define('WRITE', '31'); // for write permission to the page.
   define('DELETE', '32'); // for delete permission to the page.
   define('ADDNEW', '33'); // for add new permission to the page.
   define('MOVE', '34'); // for move permission to the page.
   define('COPY', '35'); // for copy permission to the page.
   define('EDITHEADING', '37'); // for edit heading permission to the page.
   define('EDITPAGECONTENT', '38'); // for edit PAGECONTENT permission to the page.
   define('CHANGEPASSWORD', '40'); // for CHANGE PASSWORD permission to the page.
   define('EDITUSERMANAGEMENT', '41'); // for CHANGE PASSWORD permission to the page.
   define('EDITMYSELF', '5'); // for CHANGE PASSWORD permission to the page.
?>