pls whats wrong with my popup login script

I have a popup login script in which once a visitor clicks on LOGIN link on any page, login form will popup. The script is as below.

<style type="text/css">
   #popupbox{
   margin: 0; 
   margin-left: 40%; 
   margin-right: 40%;
   margin-top: 50px; 
   padding-top: 10px; 
   width: 20%; 
   height: 150px; 
   position: absolute; 
   background: #FBFBF0; 
   border: solid #000000 2px; 
   z-index: 9; 
   font-family: arial; 
   visibility: hidden; 
   }
   </style>
   <script language="JavaScript" type="text/javascript">
   function login(showhide){
     if(showhide == "show"){
         document.getElementById('popupbox').style.visibility="visible";
     }else if(showhide == "hide"){
         document.getElementById('popupbox').style.visibility="hidden"; 
     }
   }
   </script>

 <div id="popupbox"> 
<?php
if(isset($_POST[Submit11])){
$email=stripslashes($_POST[email]);
$pword=stripslashes($_POST[pword]);
$pw=md5($pword);

if($email=="") echo "Enter your Email.<br>";
elseif($pword=="")  echo "Enter your Password.<br>";
else { echo "<b>Welcome</b><br>";
echo "<meta http-equiv='refresh', content='2'>";}
}
?>
 <form name="login" action="" method="post">
 <center>Username:</center>
 <center><input name="username" size="14" /></center>
 <center>Password:</center>
 <center><input name="password" type="password" size="14" /></center>
 <center><input type="submit" name="submit" value="login" /></center>
 </form>
 <br />
 <center><a href="javascript:login('hide');">close</a></center> 
 </div>

 <a href="javascript:login('show');">login</a>

PHP:

My problem here is that once the visitor clicks on "login" button on the pop up window without entering his username or password, the window will just disappear instead of echoing "Enter your Username or password". Also if the member enters his username and password correctly, the window will just disappear instead of echoing welcome and refresh the page on which the member clicked login.

Pls what do I do wrong. Thanks

 

Wrong here

if(isset($_POST[Submit11])){

and here

<input type="submit" name="submit" value="login" />

 

Thanks Kids. I have corrected as below

if(isset($_POST[submit11])){
$email=stripslashes($_POST);
$pword=stripslashes($_POST[pword]);
$pw=md5($pword);

if($email=="") echo "<span class='red'>Enter your Email.</span><br>";
elseif($pword=="") echo "<span class='red'>Enter your Password.</span><br>";
else echo "<span class='green'><b>Welcome</b></span><br>";
}
?>
<form name="login" action="" method="post">
<center>Email:</center>
<center><input name="email" size="14" /></center>
<center>Password:</center>
<center><input name="pword" type="password" size="14" /></center>
<center><input type="submit" name="submit11" value="login" /></center>
</form>

but still doing the same thing (disappearing). what else?

 

<center><input type="submit" name="submit11" value="login" /></center>

Code (markup):

to

<center><input type="submit" value="login" /></center>
<input type="hidden" name="submit11" value="login" />

Code (markup):