<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!DOCTYPE html>
<html lang="es">
<head>
<title>Formulario de sesion</title>
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css">
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/v4-shims.css">
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
</head>
<body>
<div id="form">
<div id="content">
<center>
<div class="icon">
<i class="material-icons">account_circle</i>
<h4>LOGIN IN</h4>
</div>
</center>
<form action="" method="POST" id="formu">
<span><i class="fas fa-user"></i> <input type="text" name="user" placeholder="Usuario" required/></span><br>
<input type="password" name="pass" placeholder="Password" required/>
<center><button type="submit">INGRESAR</button></center>
</form>
</div>
</div>