Untitled

<?php

?>
<!DOCTYPE html>
<html>
<center>
<head>
<meta charset="utf-8">
<title>Login</title>
<link rel="stylesheet" href="style.css" />
</head>
<body>
<?php
require('db.php');
session_start();
// If form submitted, insert values into the database.
if (isset($_POST['username'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];
    $username = stripslashes($username);
    $username = mysql_real_escape_string($username);
    $password = stripslashes($password);
    $password = mysql_real_escape_string($password);
    //Checking is user existing in the database or not
    $query    = "SELECT * FROM `users` WHERE username='$username' and password='" . md5($password) . "'";
    $result = mysql_query($query) or die(mysql_error());
    $rows = mysql_num_rows($result);
    if ($rows == 1) {
        $_SESSION['username'] = $username;
        header("Location: index.php"); // Redirect user to index.php
    } else {
        echo "<div class='form'><h3>Username/password is incorrect.</h3><br/>Click here to <a href='login.php'>Login</a></div>";
    }
} else {
?>
<div class="form">
<body style="margin-top: 5cm;">
<body bgcolor="#E6E6FA">
<img src="lock_image.png" alt="Lock Image" style="width:90px;height:90px;">
<font face="verdana" color="grey"><h1>LOG IN</h1></font>
<form action="" method="post" name="login">
<input type="text" name="username" placeholder="Username" required />
<input type="password" name="password" placeholder="Password" required />
<input name="submit" type="submit" value="Login" />
</form>
<p style="font-family:verdana;">Not registered yet? <br ><a href='registration.php'>Register Here</a></p>
</div>
<?php
}
?>
</center>
</body>
</html>