Index?

[KeyIDentity]

So I have feverything on this scriot working fine, data is even going to the DB, my issue is an undefined index... Im too new it seems to understand how to define the index or what it is for that matter. Please explain in ENGLISH not php lang. how to solve this notice and would the notice show up on the web once I upload to the net?
It's line 6, the if(!$_POST['submit']){

<?php
include_once "functions.php";

connect();

if(!$_POST['submit']){
    echo "<table border=\"0\" align=\"center\" cellspacing=\"3\" cellpadding=\"3\">\n";
    echo "<form method=\"post\" action=\"register.php\">\n";
    echo "<tr><td colspan=\"2\" align=\"center\">Registration Form</td></tr>\n";
    echo "<tr><td>KeyIDentitY</td><td><input type=\"text\" name=\"username\"></td></tr>\n";
    echo "<tr><td>Password</td><td><input type=\"password\" name=\"password\"></td></tr>\n";
    echo "<tr><td>Confirm</td><td><input type=\"password\" name=\"passconf\"></td></tr>\n";
    echo "<tr><td>E-Mail</td><td><input type=\"text\" name=\"email\"></td></tr>\n";
    echo "<tr><td>Full Name</td><td><input type=\"text\" name=\"name\"></td></tr>\n";
    echo "<tr><td>Blackberry PIN</td><td><input type=\"text\" name=\"aim\"></td></tr>\n";
    echo "<tr><td colspan=\"2\" align=\"center\"><input type=\"submit\" name=\"submit\" value=\"Register\"></td></tr>\n";
    echo "</form></table>\n";
}else {
    $username = protect($_POST['username']);
    $password = protect($_POST['password']);
    $confirm = protect($_POST['passconf']);
    $email = protect($_POST['email']);
    $name = protect($_POST['name']);
    $aim = protect($_POST['aim']);

$errors = array();

    if(!$username){
        $errors[] = "Username is not defined!";
    }

    if(!$password){
        $errors[] = "Password is not defined!";
    }

    if($password){
        if(!$confirm){
            $errors[] = "Confirmation password is not defined!";
        }
    }

    if(!$email){
        $errors[] = "E-mail is not defined!";
    }

    if(!$name){
        $errors[] = "Name is not defined!";
    }

    if(!$aim){
        $errors[] = "AIM Screename is not defined!";
    }

    if($username){
        if(!ctype_alnum($username)){
            $errors[] = "Username can only contain numbers and letters!";
        }

        $range = range(1,32);
        if(!in_array(strlen($username),$range)){
            $errors[] = "Username must be between 1 and 32 characters!";
        }
    }

    if($password && $confirm){
        if($password != $confirm){
            $errors[] = "Passwords do not match!";
        }
    }

    if($email){
        $checkemail = "/^[a-z0-9]+([_\\.-][a-z0-9]+)*@([a-z0-9]+([\.-][a-z0-9]+)*)+\\.[a-z]{2,}$/i";
        if(!preg_match($checkemail, $email)){
            $errors[] = "E-mail is not valid, must be [e-mail]!";
        }
    }

    if($name){
        $range2 = range(3,64);
        if(!in_array(strlen($name),$range2)){
            $errors[] = "Your name must be between 3 and 64 characters!";
        }
    }

    if($aim){
        $range3 = range(3,16);
        if(!in_array(strlen($aim),$range3)){
            $errors[] = "Your AIM screenname must be between 3 and 16 characters!";
        }
    }

    if($username){
        $sql = "SELECT * FROM `users` WHERE `username`='".$username."'";
        $res = mysql_query($sql) or die(mysql_error());

            if(mysql_num_rows($res) > 0){
                $errors[] = "The username you supplied is already in use!";
            }
    }

    if($email){
        $sql2 = "SELECT * FROM `users` WHERE `email`='".$email."'";
        $res2 = mysql_query($sql2) or die(mysql_error());

            if(mysql_num_rows($res2) > 0){
                $errors[] = "The e-mail address you supplied is already in use of another user!";
            }
    }

    if($aim){
        $sql3 = "SELECT * FROM `users` WHERE `aim`='{$aim}'";
        $res3 = mysql_query($sql3) or die(mysql_error());

            if(mysql_num_rows($res3) > 0){
                $errors[] = "The AIM screenname you supplied is already in use of another user!";
            }
    }

    if(count($errors) > 0){
        foreach($errors AS $error){
            echo $error . "<br>\n";
        }
    }else {
        $sql4 = "INSERT INTO `users`
                (`username`,`password`,`email`,`name`,`aim`,`admin`,`time`)
                VALUES ('".$username."','".md5($password)."','".$email."','".$name."','".$aim."','0','".time()."')";
        $res4 = mysql_query($sql4) or die(mysql_error());
        echo "You have successfully registered with the username <b>".$username."</b> and the password of <b>".$password."</b>!";
    }
}

?>  

[Krik]

how to solve this notice and would the notice show up on the web once I upload
to the net?

First you can change what error messages are displayed by changing the settings in php.ini or by using [man]error_reporting[/man]. It is good technique to never let error messages be seen by the user. Usually you will want to use user friendly error reporting. Also you should note that you have the error reporting set to the highest level to get that error.

To fix the problem

if(!isset($_POST['submit']))

[KeyIDentity]

THANKS YOU!!!!! ALL ERRORS ARE GONE!!!! ITS WORKING GREAT... Just some formatting/layout help needed from here... THANK YOU AGAIN!