HTML:

<?php
$page_title = 'The Pie - Welcome';
$page_desc = 'Welcome to The Pie blog';
$page_keyw = 'the,pie,welcome,login,sign,up,blog';
include ('header.php');
?>

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

<div class="container text-center">
	<div class="row">
		<div class="col-md-6">
			<form method="post">
        		<?php include('../php/errors.php'); ?>
        		<p>Username:</p>
           		<input type="text" name="username" >
            	<br>
            	<p>Password:</p>
            	<input type="password" name="password">
            	<br>
            	<br>
            	<button type="submit" class="btn" name="login_user">Login</button>
    		</form>
		</div>
		<hr class="hr-r">
		<div class="col-md-6">
			<form method="post">
        		<?php include('../php/errors.php'); ?>
            	<p>Username:</p>
            	<input type="text" placeholder="Example" name="username" value="<?php echo $username; ?>">
            	<p>Email:</p>
            	<input type="email" placeholder="example@mail.com" name="email" value="<?php echo $email; ?>">
            	<p>Password:</p>
            	<input type="password" name="password_1" placeholder="*************">
            	<p>Confirm password:</p>
            	<input type="password" name="password_2" placeholder="*************">
            	<br>
            	<br>
            	<button type="submit" class="btn" name="reg_user">Register</button>
        	</form>
		</div>
	</div>
</div>

<!-- FOOTER -->
<?php
include ('footer.php');
?>

CSS:

@charset "utf-8";
@media screen and (max-width: 767px){
	.hr-r{
		width: 220px;
		border: solid black 1px;
	}
}

@media screen and (min-width: 768px){
	.hr-r{
		height: 10px;
		border: solid black 1px;
	}
}