I have the following two _forms:
user form
<%= simple_form_for(@user, :url => @target) do |f| %>
<% if @user.errors.any? %
Just add error: false to your inputs this will not clear the css but will clear the inline errors
f.input error: false or :error => false
Edit:
From http://ruby.railstutorial.org/book/ruby-on-rails-tutorial
/app/views/shared/_error_messages.html.erb
<% if object.errors.any? %>
<div id="error_explanation">
<div class="alert alert-error">
The form contains <%= pluralize(object.errors.count, "error") %>.
</div>
<ul>
<% object.errors.full_messages.each do |msg| %>
<li>* <%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
in VIEW
<%= form_for(@user) do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<%= f.label :name %>
<%= f.text_field :name %>
<%= f.label :email %>
<%= f.text_field :email %>
<%= f.label :password %>
<%= f.password_field :password %>
<%= f.label :password_confirmation, "Confirmation" %>
<%= f.password_field :password_confirmation %>
<%= f.submit "Create my account", class: "btn btn-large btn-primary" %>
<% end %>