app/views/devise/sessions/new.html.erb
<% content_for :title_bar do %>
<span class="navbar-brand"><%= t('login') %></span>
<% end %>
<div class="container">
<div class="row">
<div class="col-sm-12 col-md-6 col-lg-4 col-md-offset-3 col-lg-offset-4">
<h3 class="auth-welcome text-center"><%= t('welcome') %></h3>
<div class="auth-wrapper">
<%= form_for(resource, as: resource_name, url: session_path(resource_name), html: { class: 'form-horizontal' }) do |f| %>
<div class="auth-form-group">
<%= f.label :email, class: 'sr-only' %>
<%= f.email_field :email, autofocus: true, placeholder: true, class: 'form-control auth-form-control' %>
</div>
<div class="auth-form-group">
<%= f.label :password, class: 'sr-only' %>
<%= f.password_field :password, autocomplete: 'off', placeholder: true, class: 'form-control auth-form-control' %>
</div>
<% if devise_mapping.rememberable? -%>
<div class="auth-form-group">
<div class="checkbox auth-form-checkbox">
<label>
<%= f.check_box :remember_me %> <%= f.label :remember_me, class: 'auth-form-checkbox-label' %>
</label>
</div>
</div>
<% end -%>
<div class="actions clearfix">
<%= f.submit t('.sign_in'), class: 'btn btn-primary pull-right auth-button-submit' %>
</div>
<% end %>
</div>
</div>
<div class="clearfix"></div>
<div class="col-sm-12 col-md-6 col-lg-4 col-md-offset-3 col-lg-offset-4">
<%= render 'devise/shared/links' %>
</div>
</div>
</div>