This is very minor, but to help encourage best practises it'd be best to have the input type 'email' for this email input example instead of 'text'
<form class="form-signin" role="form">
<h2 class="form-signin-heading">Please sign in</h2>
- <input type="text" class="form-control" placeholder="Email address" required autofocus>
+ <input type="email" class="form-control" placeholder="Email address" required autofocus>
<input type="password" class="form-control" placeholder="Password" required>
<label class="checkbox">
<input type="checkbox" value="remember-me"> Remember me