diff --git a/.rubocop.yml b/.rubocop.yml
index 5b39c3c..6b2cafe 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -16,8 +16,13 @@ Metrics/LineLength:
 
 Metrics/ClassLength:
   Exclude:
+    - 'spec/support/gem_test_helpers.rb'
     - 'lib/cybele/generators/app_generator.rb'
 
+Metrics/ModuleLength:
+  Exclude:
+    - 'spec/support/gem_test_helpers.rb'
+
 Style/AccessorMethodName:
   Exclude:
     - 'lib/cybele/generators/app_generator.rb'
@@ -25,6 +30,13 @@ Style/AccessorMethodName:
 Metrics/MethodLength:
   CountComments: false
   Max: 15
+  Exclude:
+    - 'spec/support/gem_test_helpers.rb'
+
+Metrics/AbcSize:
+  Exclude:
+    - 'spec/support/gem_test_helpers.rb'
+    - 'spec/support/mail_test_helpers.rb'
 
 Metrics/BlockLength:
   CountComments: false
@@ -35,6 +47,7 @@ Metrics/BlockLength:
     - 'spec/**/*.rb'
     - 'lib/cybele/app_builder.rb'
     - 'lib/cybele/generators/app_generator.rb'
+    - 'spec/support/cybele_test_helpers.rb'
 
 Style/FrozenStringLiteralComment:
   EnforcedStyle: when_needed
diff --git a/lib/cybele.rb b/lib/cybele.rb
index 08f5805..e25b2d5 100644
--- a/lib/cybele.rb
+++ b/lib/cybele.rb
@@ -15,4 +15,5 @@
 require 'cybele/helpers/mailer'
 require 'cybele/helpers/paperclip'
 require 'cybele/helpers/devise'
+require 'cybele/helpers/error_pages'
 require 'cybele/app_builder'
diff --git a/lib/cybele/app_builder.rb b/lib/cybele/app_builder.rb
index 3026c1b..1ba402f 100644
--- a/lib/cybele/app_builder.rb
+++ b/lib/cybele/app_builder.rb
@@ -15,6 +15,7 @@ class AppBuilder < Rails::AppBuilder
     include Cybele::Helpers::Mailer
     include Cybele::Helpers::Paperclip
     include Cybele::Helpers::Devise
+    include Cybele::Helpers::ErrorPages
 
     def readme
       template 'README.md.erb',
@@ -75,7 +76,7 @@ def setup_gitignore_files
     end
 
     def setup_gitignore_folders
-      %w(
+      %w[
         app/assets/images
         db/migrate
         spec/support
@@ -84,7 +85,7 @@ def setup_gitignore_folders
         spec/views
         spec/controllers
         spec/helpers
-      ).each do |dir|
+      ].each do |dir|
         empty_directory_with_keep_file dir
       end
     end
diff --git a/lib/cybele/generators/app_generator.rb b/lib/cybele/generators/app_generator.rb
index 51a9b5a..9d2ff6c 100644
--- a/lib/cybele/generators/app_generator.rb
+++ b/lib/cybele/generators/app_generator.rb
@@ -213,6 +213,11 @@ def gitignore_files_and_folders
       build :setup_gitignore_folders
     end
 
+    def configure_error_pages
+      say 'Setup custom exception pages and 404 page'
+      build :configure_error_pages
+    end
+
     def goodbye
       say 'Congratulations! That\'s all...', :green
     end
diff --git a/lib/cybele/helpers/error_pages.rb b/lib/cybele/helpers/error_pages.rb
new file mode 100644
index 0000000..9baeb83
--- /dev/null
+++ b/lib/cybele/helpers/error_pages.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module Cybele
+  module Helpers
+    module ErrorPages
+      def configure_error_pages
+        inject_into_file 'app/controllers/application_controller.rb',
+                         template_content('error_pages/error_control.erb'),
+                         before: 'self.responder'
+
+        inject_into_file 'app/controllers/application_controller.rb',
+                         template_content('error_pages/error_method.erb'),
+                         after: 'protect_from_forgery with: :exception'
+
+        inject_into_file 'config/routes.rb',
+                         template_content('error_pages/error_route.erb'),
+                         before: /^end/
+
+        create_error_pages_files
+      end
+
+      private
+
+      def create_error_pages_files
+        # Server Error
+        template 'error_pages/internal_server_error.html.haml',
+                 'app/views/errors/internal_server_error.html.haml',
+                 force: true
+
+        # Not Found Error
+        template 'error_pages/not_found.html.haml',
+                 'app/views/errors/not_found.html.haml',
+                 force: true
+      end
+    end
+  end
+end
diff --git a/spec/features/new_default_project_spec.rb b/spec/features/new_default_project_spec.rb
index 3c41e1b..77f54d5 100644
--- a/spec/features/new_default_project_spec.rb
+++ b/spec/features/new_default_project_spec.rb
@@ -31,7 +31,7 @@
     expect(gemfile_file).to match(/^gem 'devise-async'/)
 
     sidekiq_file = content('config/sidekiq.yml')
-    expect(sidekiq_file).to match(/^:concurrency: 25/)
+    expect(sidekiq_file).to match('[high_priority, 2]')
 
     sidekiq_schedule_file = content('config/sidekiq_schedule.yml')
     expect(sidekiq_schedule_file).to match(/-> Daily at midnight/)
@@ -207,4 +207,12 @@
   it 'uses devise' do
     devise_test_helper
   end
+
+  it 'uses error_pages' do
+    error_pages_helper
+  end
+
+  it 'uses gitignore' do
+    gitignore_helper
+  end
 end
diff --git a/spec/features/new_not_default_project_spec.rb b/spec/features/new_not_default_project_spec.rb
index 8bb6500..1ce0eb7 100644
--- a/spec/features/new_not_default_project_spec.rb
+++ b/spec/features/new_not_default_project_spec.rb
@@ -187,4 +187,12 @@
   it 'uses devise' do
     devise_test_helper
   end
+
+  it 'uses error_pages' do
+    error_pages_helper
+  end
+
+  it 'uses gitignore' do
+    gitignore_helper
+  end
 end
diff --git a/spec/support/gem_test_helpers.rb b/spec/support/gem_test_helpers.rb
index 71a60b2..049c582 100644
--- a/spec/support/gem_test_helpers.rb
+++ b/spec/support/gem_test_helpers.rb
@@ -145,4 +145,23 @@ def config_test_helper
     config_test_file = content('config/environments/test.rb')
     expect(config_test_file).to match(/^Rails.application.configure/)
   end
+
+  def error_pages_helper
+    application_controller_file = content('app/controllers/application_controller.rb')
+    expect(application_controller_file).to match('rescue_from Exception')
+    expect(application_controller_file).to match('rescue_from ActiveRecord::RecordNotFound')
+    expect(application_controller_file).to match('rescue_from ActionController::RoutingError')
+    expect(application_controller_file).to match('server_error')
+    expect(application_controller_file).to match('page_not_found')
+
+    route_file = content('config/routes.rb')
+    expect(route_file).to match('unmatched_route')
+  end
+
+  def gitignore_helper
+    application_controller_file = content('.gitignore')
+    expect(application_controller_file).to match('.DS_Store')
+    expect(application_controller_file).to match('.secret')
+    expect(application_controller_file).to match('.env')
+  end
 end
diff --git a/spec/support/mail_test_helpers.rb b/spec/support/mail_test_helpers.rb
index 80d4b0a..031dbe2 100644
--- a/spec/support/mail_test_helpers.rb
+++ b/spec/support/mail_test_helpers.rb
@@ -10,8 +10,6 @@ def mail_test_helper(path)
     expect(file).to match('user_name:')
     expect(file).to match('password:')
     expect(file).to match('authentication:')
-    unless content('config/settings.yml').present?
-      expect(file).to match('host:')
-    end
+    expect(file).to match('host:') unless content('config/settings.yml').present?
   end
 end
diff --git a/templates/config/locales/view.en.yml b/templates/config/locales/view.en.yml
index 5029022..3373fc5 100644
--- a/templates/config/locales/view.en.yml
+++ b/templates/config/locales/view.en.yml
@@ -1,2 +1,5 @@
 en:
-  view:
\ No newline at end of file
+  view:
+    error:
+      internal_server_error: "We are sorry. An error occured. Our engineers are working on it. We will solve it as soon as possible."
+      not_found: "We are sorry. Page was not found. It may have been moved."
\ No newline at end of file
diff --git a/templates/config/locales/view.tr.yml b/templates/config/locales/view.tr.yml
index 7df91e5..ce108f7 100644
--- a/templates/config/locales/view.tr.yml
+++ b/templates/config/locales/view.tr.yml
@@ -1,2 +1,5 @@
 tr:
-  view:
\ No newline at end of file
+  view:
+    error:
+      internal_server_error: "Üzgünüz. Şu anda bir hata var. Mühendislerimiz bu hata üzerinde çalışma yapıyorlar. En kısa sürede çözeceğiz."
+      not_found: "Üzgünüz. Bu sayfa bulunamadı. Taşınmış olabilir. Buraya gitmek istediğinizden emin olun."
\ No newline at end of file
diff --git a/templates/error_pages/error_control.erb b/templates/error_pages/error_control.erb
new file mode 100644
index 0000000..a5dff31
--- /dev/null
+++ b/templates/error_pages/error_control.erb
@@ -0,0 +1,5 @@
+
+  rescue_from Exception, with: :server_error if Rails.env.production? or Rails.env.staging?
+  rescue_from ActiveRecord::RecordNotFound, with: :page_not_found if Rails.env.production? or Rails.env.staging?
+  rescue_from ActionController::RoutingError, with: :page_not_found if Rails.env.production? or Rails.env.staging?
+
diff --git a/templates/error_pages/error_method.erb b/templates/error_pages/error_method.erb
new file mode 100644
index 0000000..6f3d741
--- /dev/null
+++ b/templates/error_pages/error_method.erb
@@ -0,0 +1,10 @@
+
+
+  def server_error(exception)
+    Rollbar.error "ApplicationController#server_error --exception: #{exception}"
+    render template: 'errors/internal_server_error', status: 500
+  end
+
+  def page_not_found
+    render template: 'errors/not_found', status: 404
+  end
diff --git a/templates/error_pages/error_route.erb b/templates/error_pages/error_route.erb
new file mode 100644
index 0000000..4732d9c
--- /dev/null
+++ b/templates/error_pages/error_route.erb
@@ -0,0 +1,4 @@
+
+  if Rails.env.production? or Rails.env.staging?
+    match '*unmatched_route', to: 'application#page_not_found', via: :all
+  end
diff --git a/templates/error_pages/internal_server_error.html.haml b/templates/error_pages/internal_server_error.html.haml
new file mode 100644
index 0000000..54c4307
--- /dev/null
+++ b/templates/error_pages/internal_server_error.html.haml
@@ -0,0 +1,2 @@
+.well
+  %p= t('view.internal_server_error')
\ No newline at end of file
diff --git a/templates/error_pages/not_found.html.haml b/templates/error_pages/not_found.html.haml
new file mode 100644
index 0000000..cc9239c
--- /dev/null
+++ b/templates/error_pages/not_found.html.haml
@@ -0,0 +1,2 @@
+.well
+  %p= t('view.not_found')
\ No newline at end of file