production.log当所有给我的都是这个时，我该如何去追踪错误？
11: <%= javascript_include_tag "application" %>
12: <%= csrf_meta_tags %>
13: <%= yield(:head) %>
app/views/layouts/application.html.erb:10:in `_app_views_layouts_application_html_erb__4417234491726047977_45250520'
app/controllers/docs_controller.rb:27:in `index'
Processing by ErrorsController#broken as HTML
Rendered errors/broken.html.erb within layouts/application (0.5ms)
Completed 500 Internal Server Error in 16ms
仅供参考：第 10 行application.html.erb是<%= stylesheet_link_tag "application", :media => "all" %>所以我假设它与我的 CSS 或我的 gemfile 有关。我该如何进一步调查？
另外，我的gemfile：
source 'https://rubygems.org'
gem 'rails', '3.2.12'
gem 'json', '1.7.7'
gem 'mysql2'
group :assets do
gem 'coffee-rails'
end
group :development do
gem 'better_errors'
gem 'binding_of_caller'
gem 'meta_request'
end
group :development, :test do
gem 'rspec-rails'
gem 'steak'
gem 'factory_girl_rails'
end
gem 'sass'
gem 'less-rails'
gem 'less-rails-bootstrap'
gem 'jquery-rails'
gem 'devise', '>= 2.1.2'
gem 'cancan'
gem 'paperclip', '~> 3.0'
gem 'therubyracer'
gem 'yaml_db'
gem 'passenger'
gem 'capistrano'
gem 'prawn'
gem 'bootstrap-wysihtml5-rails'
gem 'turbolinks'
gem 'jquery-turbolinks'
gem 'kaminari'
gem 'truncate_html'
gem 'rails3-jquery-autocomplete'
gem 'whenever'
gem 'impressionist'
gem 'acts_as_list'
gem 'acts_as_indexed'
gem 'state_machine'
gem 'exception_notification'
gem 'public_activity'