User Registration...

I wrote this simple script. But I can't find where is the bug.
Please note it for me.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

        <title>User Management System (Tom Cameron for NetTuts)</title>

        <link rel="stylesheet" href="style.css" type="text/css" />

        <?php include "base.php"; ?> 

    </head>

    <body>

        <div id="main">

        <?php

        if(!empty($_SESSION['LoggedIn']) && !empty ($_SESSION['Username']))

        {


        }

            ?>

        <h1>Memebers area</h1>

        <p>Thank you for logging in!</p>

        

        <?php

        elseif(!empty($_POST['username']) && !empty($_POST['password']))

        {

            $username = mysql_real_escape_string($_POST['username']);

            $password = mysql_real_escape_string($_POST['password']);


            $checklogin = mysql_query("SELECT * FROM users WHERE Username=".$username."AND Password".$password);


            if(mysql_num_rows($checklogin) == 1){

                $row = mysql_fetch_array($checklogin);

                $email = $row['EmailAddress'];

                $_SESSION['Username'] = $username;

                $_SESSION['EmailAddress'] = $email;

                $_SESSION['LoggedIn'] = 1;


                echo "<h1>Success</h1>";

                echo "<p>We are now redirecting you to the members area.</p>";

            }

 else

    {


                    echo "<h1>Error</h1>";


                    echo "<p>Sorry, your account could not be found. Please <a href=\"index.php\">click here to try again</a>.</p>";


    }


        

        

else

{


        ?>


           <h1>Member Login</h1>


           <p>Thanks for visiting! Please either login below, or <a href="register.php">click here to register</a>.</p>


            <form method="post" action="index.php" name="loginform" id="loginform">

            <fieldset>

                <label for="username">Username:</label><input type="text" name="username" id="username" /><br />

                <label for="password">Password:</label><input type="password" name="password" id="password" /><br />

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

            </fieldset>

            </form>


<?php


            }


?>


</div>

</body>

</html>