16 files changed, 94 insertions, 162 deletions
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index 52571fab60..a678dd9d90 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -7,7 +7,6 @@ Highlights in Rails 4.0:
 * Strong Parameters
 * Turbolinks
 * Russian Doll Caching
-* Asynchronous Mailers
 
 These release notes cover only the major changes. To know about various bug fixes and changes, please refer to the change logs or check out the [list of commits](https://github.com/rails/rails/commits/master) in the main Rails repository on GitHub.
 
@@ -150,7 +149,7 @@ Please refer to the [Changelog](https://github.com/rails/rails/blob/master/activ
 Action Pack
 -----------
 
-Please refer to the [Changelog](https://github.com/rails/rails/blob/master/railties/CHANGELOG.md) for detailed changes.
+Please refer to the [Changelog](https://github.com/rails/rails/blob/master/actionpack/CHANGELOG.md) for detailed changes.
 
 ### Notable changes
 
@@ -162,7 +161,7 @@ Please refer to the [Changelog](https://github.com/rails/rails/blob/master/railt
 Active Record
 -------------
 
-Please refer to the [Changelog](https://github.com/rails/rails/blob/master/railties/CHANGELOG.md) for detailed changes.
+Please refer to the [Changelog](https://github.com/rails/rails/blob/master/activerecord/CHANGELOG.md) for detailed changes.
 
 ### Notable changes
 
diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index cc80334af3..7260a48c8c 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -58,7 +58,7 @@ Parameters
 You will probably want to access data sent in by the user or other parameters in your controller actions. There are two kinds of parameters possible in a web application. The first are parameters that are sent as part of the URL, called query string parameters. The query string is everything after "?" in the URL. The second type of parameter is usually referred to as POST data. This information usually comes from an HTML form which has been filled in by the user. It's called POST data because it can only be sent as part of an HTTP POST request. Rails does not make any distinction between query string parameters and POST parameters, and both are available in the `params` hash in your controller:
 
 ```ruby
-class ClientsController < ActionController::Base
+class ClientsController < ApplicationController
   # This action uses query string parameters because it gets run
   # by an HTTP GET request, but this does not make any difference
   # to the way in which the parameters are accessed. The URL for
@@ -479,7 +479,7 @@ In addition to "before" filters, you can also run filters after an action has be
 For example, in a website where changes have an approval workflow an administrator could be able to preview them easily, just apply them within a transaction:
 
 ```ruby
-class ChangesController < ActionController::Base
+class ChangesController < ApplicationController
   around_action :wrap_in_transaction, only: :show
 
   private
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 3a9a4e73a6..513ae1272f 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -576,6 +576,8 @@ end
 
 In the test we send the email and store the returned object in the `email` variable. We then ensure that it was sent (the first assert), then, in the second batch of assertions, we ensure that the email does indeed contain what we expect.
 
+NOTE: The `ActionMailer::Base.deliveries` array is only reset automatically in `ActionMailer::TestCase` tests. If you want to have a clean slate outside Action Mailer tests, you can reset it manually with: `ActionMailer::Base.deliveries.clear`
+
 Intercepting Emails
 -------------------
 There are situations where you need to edit an email before it's delivered. Fortunately Action Mailer provides hooks to intercept every email. You can register an interceptor to make modifications to mail messages right before they are handed to the delivery agents.
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index 062bcd49f4..69d7333e6f 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -1,6 +1,6 @@
 Active Record Basics
 ====================
-
+ 
 This guide is an introduction to Active Record.
 
 After reading this guide, you will know:
diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md
index 3747b00b82..516457bcd3 100644
--- a/guides/source/active_record_callbacks.md
+++ b/guides/source/active_record_callbacks.md
@@ -157,7 +157,6 @@ The following methods trigger callbacks:
 * `save!`
 * `save(validate: false)`
 * `toggle!`
-* `update`
 * `update_attribute`
 * `update`
 * `update!`
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index fffa31927d..e939606c88 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -37,9 +37,9 @@ You should use the defaults for all new applications unless you have a specific
 
 ### Main Features
 
-The first feature of the pipeline is to concatenate assets. This is important in a production environment, because it can reduce the number of requests that a browser must make to render a web page. Web browsers are limited in the number of requests that they can make in parallel, so fewer requests can mean faster loading for your application.
+The first feature of the pipeline is to concatenate assets. This is important in a production environment, because it can reduce the number of requests that a browser makes to render a web page. Web browsers are limited in the number of requests that they can make in parallel, so fewer requests can mean faster loading for your application.
 
-Rails 2.x introduced the ability to concatenate JavaScript and CSS assets by placing `:cache => true` at the end of the `javascript_include_tag` and `stylesheet_link_tag` methods. But this technique has some limitations. For example, it cannot generate the caches in advance, and it is not able to transparently include assets provided by third-party libraries.
+Rails 2.x introduced the ability to concatenate JavaScript and CSS assets by placing `cache: true` at the end of the `javascript_include_tag` and `stylesheet_link_tag` methods. But this technique has some limitations. For example, it cannot generate the caches in advance, and it is not able to transparently include assets provided by third-party libraries.
 
 Starting with version 3.1, Rails defaults to concatenating all JavaScript files into one master `.js` file and all CSS files into one master `.css` file. As you'll learn later in this guide, you can customize this strategy to group files any way you like. In production, Rails inserts an MD5 fingerprint into each filename so that the file is cached by the web browser. You can invalidate the cache by altering this fingerprint, which happens automatically whenever you change the file contents.
 
@@ -369,8 +369,8 @@ If any of the files in the manifest have changed between requests, the server re
 Debug mode can also be enabled in the Rails helper methods:
 
 ```erb
-<%= stylesheet_link_tag "application", :debug => true %>
-<%= javascript_include_tag "application", :debug => true %>
+<%= stylesheet_link_tag "application", debug: true %>
+<%= javascript_include_tag "application", debug: true %>
 ```
 
 The `:debug` option is redundant if debug mode is on.
@@ -445,7 +445,7 @@ NOTE. If you are precompiling your assets locally, you can use `bundle install -
 The default matcher for compiling files includes `application.js`, `application.css` and all non-JS/CSS files (this will include all image assets automatically):
 
 ```ruby
-[ Proc.new{ |path| !%w(.js .css).include?(File.extname(path)) }, /application.(css|js)$/ ]
+[ Proc.new { |path| !%w(.js .css).include?(File.extname(path)) }, /application.(css|js)$/ ]
 ```
 
 NOTE. The matcher (and other members of the precompile array; see below) is applied to final compiled file names. This means that anything that compiles to JS/CSS is excluded, as well as raw JS/CSS files; for example, `.coffee` and `.scss` files are **not** automatically included as they compile to JS/CSS.
@@ -460,7 +460,7 @@ Or you can opt to precompile all assets with something like this:
 
 ```ruby
 # config/environments/production.rb
-config.assets.precompile << Proc.new { |path|
+config.assets.precompile << Proc.new do |path|
   if path =~ /\.(css|js)\z/
     full_path = Rails.application.assets.resolve(path).to_path
     app_assets_path = Rails.root.join('app', 'assets').to_path
@@ -474,7 +474,7 @@ config.assets.precompile << Proc.new { |path|
   else
     false
   end
-}
+end
 ```
 
 NOTE. Always specify an expected compiled filename that ends with js or css, even if you want to add Sass or CoffeeScript files to the precompile array.
@@ -502,14 +502,14 @@ For Apache:
 
 ```apache
 # The Expires* directives requires the Apache module `mod_expires` to be enabled.
-<LocationMatch "^/assets/.*$">
+<Location /assets/>
   # Use of ETag is discouraged when Last-Modified is present
   Header unset ETag
   FileETag None
   # RFC says only cache for 1 year
   ExpiresActive On
   ExpiresDefault "access plus 1 year"
-</LocationMatch>
+</Location>
 ```
 
 For nginx:
@@ -663,7 +663,7 @@ class Transformer
 end
 ```
 
-To enable this, pass a `new` object to the config option in `application.rb`:
+To enable this, pass a new object to the config option in `application.rb`:
 
 ```ruby
 config.assets.css_compressor = Transformer.new
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 0228d463cf..e52264f296 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -85,6 +85,51 @@ This fragment is then available to all actions in the `ProductsController` using
 ```ruby
 expire_fragment('all_available_products')
 ```
+If you want to avoid expiring the fragment manually, whenever an action updates a product, you can define a helper method:
+
+```ruby
+module ProductsHelper
+  def cache_key_for_products
+    count          = Product.count
+    max_updated_at = Product.maximum(:updated_at).try(:utc).try(:to_s, :number)
+    "products/all-#{count}-#{max_updated_at}"
+  end
+end
+```
+
+This method generates a cache key that depends on all products and can be used in the view:
+
+```ruby
+<% cache(cache_key_for_products) do %>
+  All available products:
+<% end %>
+```
+You can also use an Active Record model as the cache key:
+
+```ruby
+<% Product.all.each do |p| %>
+  <% cache(p) do %>
+    <%= link_to p.name, product_url(p) %>
+  <% end %>
+<% end %>
+```
+
+Behind the scenes, a method called `cache_key` will be invoked on the model and it returns a string like `products/23-20130109142513`. The cache key includes the model name, the id and finally the updated_at timestamp. Thus it will automatically generate a new fragment when the product is updated because the key changes.
+
+You can also combine the two schemes which is called "Russian Doll Caching":
+
+```ruby
+<% cache(cache_key_for_products) do %>
+  All available products:
+  <% Product.all.each do |p| %>
+    <% cache(p) do %>
+      <%= link_to p.name, product_url(p) %>
+    <% end %>
+  <% end %>
+<% end %>
+```
+
+It's called "Russian Doll Caching" because it nests multiple fragments. The advantage is that if a single product is updated, all the other inner fragments can be reused when regenerating the outer fragment.
 
 ### SQL Caching
 
@@ -93,7 +138,7 @@ Query caching is a Rails feature that caches the result set returned by each que
 For example:
 
 ```ruby
-class ProductsController < ActionController
+class ProductsController < ApplicationController
 
   def index
     # Run a find query
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index fc1d0d7530..c1f31fd2b0 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -303,7 +303,7 @@ The schema dumper adds one additional configuration option:
 
 * `config.action_controller.permit_all_parameters` sets all the parameters for mass assignment to be permitted by default. The default value is `false`.
 
-* `config.action_controller.raise_on_unpermitted_parameters` enables raising an exception if parameters that are not explicitly permitted are found. The default value is `true` in development and test environments, `false` otherwise.
+* `config.action_controller.action_on_unpermitted_params` enables logging or raising an exception if parameters that are not explicitly permitted are found. Set to `:log` or `:raise` to enable. The default value is `:log` in development and test environments, and `false` in all other environments.
 
 ### Configuring Action Dispatch
 
@@ -345,34 +345,6 @@ The schema dumper adds one additional configuration option:
 
 * `config.action_view.erb_trim_mode` gives the trim mode to be used by ERB. It defaults to `'-'`. See the [ERB documentation](http://www.ruby-doc.org/stdlib/libdoc/erb/rdoc/) for more information.
 
-* `config.action_view.javascript_expansions` is a hash containing expansions that can be used for the JavaScript include tag. By default, this is defined as:
-
-    ```ruby
-    config.action_view.javascript_expansions = { :defaults => %w(jquery jquery_ujs) }
-    ```
-
-    However, you may add to this by defining others:
-
-    ```ruby
-    config.action_view.javascript_expansions[:prototype] = [
-      'prototype', 'effects', 'dragdrop', 'controls'
-    ]
-    ```
-
-    And can reference in the view with the following code:
-
-    ```ruby
-    <%= javascript_include_tag :prototype %>
-    ```
-
-* `config.action_view.stylesheet_expansions` works in much the same way as `javascript_expansions`, but has no default key. Keys defined for this hash can be referenced in the view like such:
-
-    ```ruby
-    <%= stylesheet_link_tag :special %>
-    ```
-
-* `config.action_view.cache_asset_ids` With the cache enabled, the asset tag helper methods will make fewer expensive file system calls (the default implementation checks the file system timestamp). However this prevents you from modifying any asset files while the server is running.
-
 * `config.action_view.embed_authenticity_token_in_remote_forms` allows you to set the default behavior for `authenticity_token` in forms with `:remote => true`. By default it's set to false, which means that remote forms will not include `authenticity_token`, which is helpful when you're fragment-caching the form. Remote forms get the authenticity from the `meta` tag, so embedding is unnecessary unless you support browsers without JavaScript. In such case you can either pass `:authenticity_token => true` as a form option or set this config setting to `true`
 
 * `config.action_view.prefix_partial_path_with_controller_namespace` determines whether or not partials are looked up from a subdirectory in templates rendered from namespaced controllers. For example, consider a controller named `Admin::PostsController` which renders this template:
@@ -681,10 +653,6 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `action_dispatch.configure` Configures the `ActionDispatch::Http::URL.tld_length` to be set to the value of `config.action_dispatch.tld_length`.
 
-* `action_view.cache_asset_ids` Sets `ActionView::Helpers::AssetTagHelper::AssetPaths.cache_asset_ids` to `false` when Active Support loads, but only if `config.cache_classes` is too.
-
-* `action_view.javascript_expansions` Registers the expansions set up by `config.action_view.javascript_expansions` and `config.action_view.stylesheet_expansions` to be recognized by Action View and therefore usable in the views.
-
 * `action_view.set_configs` Sets up Action View by using the settings in `config.action_view` by `send`'ing the method names as setters to `ActionView::Base` and passing the values through.
 
 * `action_controller.logger` Sets `ActionController::Base.logger` — if it's not already set — to `Rails.logger`.
diff --git a/guides/source/development_dependencies_install.md b/guides/source/development_dependencies_install.md
index db43d62fcf..6493c1e1ec 100644
--- a/guides/source/development_dependencies_install.md
+++ b/guides/source/development_dependencies_install.md
@@ -174,6 +174,20 @@ $ cd activerecord
 $ bundle exec rake postgresql:build_databases
 ```
 
+It is possible to build databases for both PostgreSQL and MySQL with
+
+```bash
+$ cd activerecord
+$ bundle exec rake db:create
+```
+
+You can cleanup the databases using
+
+```bash
+$ cd activerecord
+$ bundle exec rake db:drop
+```
+
 NOTE: Using the rake task to create the test databases ensures they have the correct character set and collation.
 
 NOTE: You'll see the following warning (or localized warning) during activating HStore extension in PostgreSQL 9.1.x or earlier: "WARNING: => is deprecated as an operator".
diff --git a/guides/source/engines.md b/guides/source/engines.md
index f35233993c..459aa8d57e 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -261,9 +261,9 @@ end
 
 This helps prevent conflicts with any other engine or application that may have a post resource as well.
 
-Finally, two files that are the assets for this resource are generated, `app/assets/javascripts/blorgh/posts.js` and `app/assets/javascripts/blorgh/posts.css`. You'll see how to use these a little later.
+Finally, two files that are the assets for this resource are generated, `app/assets/javascripts/blorgh/posts.js` and `app/assets/stylesheets/blorgh/posts.css`. You'll see how to use these a little later.
 
-By default, the scaffold styling is not applied to the engine as the engine's layout file, `app/views/blorgh/application.html.erb` doesn't load it. To make this apply, insert this line into the `<head>` tag of this layout:
+By default, the scaffold styling is not applied to the engine as the engine's layout file, `app/views/layouts/blorgh/application.html.erb` doesn't load it. To make this apply, insert this line into the `<head>` tag of this layout:
 
 ```erb
 <%= stylesheet_link_tag "scaffold" %>
@@ -288,7 +288,7 @@ Now people will only need to go to the root of the engine to see all the posts,
 
 ### Generating a comments resource
 
-Now that the engine can to create new blog posts, it only makes sense to add commenting functionality as well. To do get this, you'll need to generate a comment model, a comment controller and then modify the posts scaffold to display comments and allow people to create new ones.
+Now that the engine can create new blog posts, it only makes sense to add commenting functionality as well. To do this, you'll need to generate a comment model, a comment controller and then modify the posts scaffold to display comments and allow people to create new ones.
 
 Run the model generator and tell it to generate a `Comment` model, with the related table having two columns: a `post_id` integer and `text` text column.
 
@@ -470,7 +470,7 @@ If you have multiple engines that need migrations copied over, use `railties:ins
 $ rake railties:install:migrations
 ```
 
-This command, when run for the first time will copy over all the migrations from the engine. When run the next time, it will only copy over migrations that haven't been copied over already. The first run for this command will output something such as this:
+This command, when run for the first time, will copy over all the migrations from the engine. When run the next time, it will only copy over migrations that haven't been copied over already. The first run for this command will output something such as this:
 
 ```bash
 Copied migration [timestamp_1]_create_blorgh_posts.rb from blorgh
@@ -754,10 +754,9 @@ end
 
 #### Implementing Decorator Pattern Using ActiveSupport::Concern
 
-Using `Class#class_eval` is great for simple adjustments, but for more complex class modifications, you might want to consider using [`ActiveSupport::Concern`](http://edgeapi.rubyonrails.org/classes/ActiveSupport/Concern.html) helps manage load order of interlinked dependencies at run time allowing you to significantly modularize your code.
+Using `Class#class_eval` is great for simple adjustments, but for more complex class modifications, you might want to consider using [`ActiveSupport::Concern`](http://edgeapi.rubyonrails.org/classes/ActiveSupport/Concern.html). ActiveSupport::Concern manages load order of interlinked dependent modules and classes at run time allowing you to significantly modularize your code.
 
-**Adding** `Post#time_since_created`<br/>
-**Overriding** `Post#summary`
+**Adding** `Post#time_since_created` and **Overriding** `Post#summary`
 
 ```ruby
 # MyApp/app/models/blorgh/post.rb
@@ -790,7 +789,7 @@ module Blorgh::Concerns::Models::Post
   extend ActiveSupport::Concern
 
   # 'included do' causes the included code to be evaluated in the
-  # conext where it is included (post.rb), rather than be 
+  # context where it is included (post.rb), rather than be 
   # executed in the module's context (blorgh/concerns/models/post).
   included do
     attr_accessor :author_name
@@ -800,9 +799,9 @@ module Blorgh::Concerns::Models::Post
 
     private
 
-    def set_author
-      self.author = User.find_or_create_by(name: author_name)
-    end
+      def set_author
+        self.author = User.find_or_create_by(name: author_name)
+      end
   end
 
   def summary
@@ -840,7 +839,7 @@ Try this now by creating a new file at `app/views/blorgh/posts/index.html.erb` a
 
 ### Routes
 
-Routes inside an engine are, by default, isolated from the application. This is done by the `isolate_namespace` call inside the `Engine` class. This essentially means that the application and its engines can have identically named routes, and that they will not clash.
+Routes inside an engine are, by default, isolated from the application. This is done by the `isolate_namespace` call inside the `Engine` class. This essentially means that the application and its engines can have identically named routes and they will not clash.
 
 Routes inside an engine are drawn on the `Engine` class within `config/routes.rb`, like this:
 
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 7c26512046..339008ab9e 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -695,72 +695,6 @@ To include `http://example.com/main.js`:
 <%= javascript_include_tag "http://example.com/main.js" %>
 ```
 
-If the application does not use the asset pipeline, the `:defaults` option loads jQuery by default:
-
-```erb
-<%= javascript_include_tag :defaults %>
-```
-
-Outputting `script` tags such as this:
-
-```html
-<script src="/javascripts/jquery.js"></script>
-<script src="/javascripts/jquery_ujs.js"></script>
-```
-
-These two files for jQuery, `jquery.js` and `jquery_ujs.js` must be placed inside `public/javascripts` if the application doesn't use the asset pipeline. These files can be downloaded from the [jquery-rails repository on GitHub](https://github.com/indirect/jquery-rails/tree/master/vendor/assets/javascripts)
-
-WARNING: If you are using the asset pipeline, this tag will render a `script` tag for an asset called `defaults.js`, which would not exist in your application unless you've explicitly created it.
-
-And you can in any case override the `:defaults` expansion in `config/application.rb`:
-
-```ruby
-config.action_view.javascript_expansions[:defaults] = %w(foo.js bar.js)
-```
-
-You can also define new defaults:
-
-```ruby
-config.action_view.javascript_expansions[:projects] = %w(projects.js tickets.js)
-```
-
-And use them by referencing them exactly like `:defaults`:
-
-```erb
-<%= javascript_include_tag :projects %>
-```
-
-When using `:defaults`, if an `application.js` file exists in `public/javascripts` it will be included as well at the end.
-
-Also, if the asset pipeline is disabled, the `:all` expansion loads every JavaScript file in `public/javascripts`:
-
-```erb
-<%= javascript_include_tag :all %>
-```
-
-Note that your defaults of choice will be included first, so they will be available to all subsequently included files.
-
-You can supply the `:recursive` option to load files in subfolders of `public/javascripts` as well:
-
-```erb
-<%= javascript_include_tag :all, recursive: true %>
-```
-
-If you're loading multiple JavaScript files, you can create a better user experience by combining multiple files into a single download. To make this happen in production, specify `cache: true` in your `javascript_include_tag`:
-
-```erb
-<%= javascript_include_tag "main", "columns", cache: true %>
-```
-
-By default, the combined file will be delivered as `javascripts/all.js`. You can specify a location for the cached asset file instead:
-
-```erb
-<%= javascript_include_tag "main", "columns",
-  cache: "cache/main/display" %>
-```
-
-You can even use dynamic paths such as `cache/#{current_site}/main/display`.
-
 #### Linking to CSS Files with the `stylesheet_link_tag`
 
 The `stylesheet_link_tag` helper returns an HTML `<link>` tag for each source provided.
@@ -797,33 +731,6 @@ By default, the `stylesheet_link_tag` creates links with `media="screen" rel="st
 <%= stylesheet_link_tag "main_print", media: "print" %>
 ```
 
-If the asset pipeline is disabled, the `all` option links every CSS file in `public/stylesheets`:
-
-```erb
-<%= stylesheet_link_tag :all %>
-```
-
-You can supply the `:recursive` option to link files in subfolders of `public/stylesheets` as well:
-
-```erb
-<%= stylesheet_link_tag :all, recursive: true %>
-```
-
-If you're loading multiple CSS files, you can create a better user experience by combining multiple files into a single download. To make this happen in production, specify `cache: true` in your `stylesheet_link_tag`:
-
-```erb
-<%= stylesheet_link_tag "main", "columns", cache: true %>
-```
-
-By default, the combined file will be delivered as `stylesheets/all.css`. You can specify a location for the cached asset file instead:
-
-```erb
-<%= stylesheet_link_tag "main", "columns",
-  cache: "cache/main/display" %>
-```
-
-You can even use dynamic paths such as `cache/#{current_site}/main/display`.
-
 #### Linking to Images with the `image_tag`
 
 The `image_tag` helper builds an HTML `<img />` tag to the specified file. By default, files are loaded from `public/images`.
diff --git a/guides/source/migrations.md b/guides/source/migrations.md
index 617e01bd15..cefbc3b829 100644
--- a/guides/source/migrations.md
+++ b/guides/source/migrations.md
@@ -474,7 +474,7 @@ class ExampleMigration < ActiveRecord::Migration
       t.references :category
     end
 
-    #add a foreign key
+    # add a foreign key
     execute <<-SQL
       ALTER TABLE products
         ADD CONSTRAINT fk_products_categories
@@ -1011,7 +1011,7 @@ with foreign key constraints in the database.
 
 Although Active Record does not provide any tools for working directly with
 such features, the `execute` method can be used to execute arbitrary SQL. You
-could also use some plugin like
+could also use some gem like
 [foreigner](https://github.com/matthuhiggins/foreigner) which add foreign key
 support to Active Record (including support for dumping foreign keys in
 `db/schema.rb`).
diff --git a/guides/source/nested_model_forms.md b/guides/source/nested_model_forms.md
index 93d8e8dfcd..b90b3bb5fc 100644
--- a/guides/source/nested_model_forms.md
+++ b/guides/source/nested_model_forms.md
@@ -98,7 +98,7 @@ A nested model form will _only_ be built if the associated object(s) exist. This
 Consider the following typical RESTful controller which will prepare a new Person instance and its `address` and `projects` associations before rendering the `new` template:
 
 ```ruby
-class PeopleController < ActionController:Base
+class PeopleController < ApplicationController
   def new
     @person = Person.new
     @person.built_address
diff --git a/guides/source/security.md b/guides/source/security.md
index 3706a61431..769bd130be 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -9,7 +9,6 @@ After reading this guide, you will know:
 * The concept of sessions in Rails, what to put in there and popular attack methods.
 * How just visiting a site can be a security problem (with CSRF).
 * What you have to pay attention to when working with files or providing an administration interface.
-* The Rails-specific mass assignment problem.
 * How to manage users: Logging in and out and attack methods on all layers.
 * And the most popular injection attack methods.
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 09d6d2d5ee..39a44794a7 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -943,7 +943,7 @@ Cheers!
 
 This is the right time to understand a little more about writing tests for your mailers. The line `ActionMailer::Base.delivery_method = :test` in `config/environments/test.rb` sets the delivery method to test mode so that email will not actually be delivered (useful to avoid spamming your users while testing) but instead it will be appended to an array (`ActionMailer::Base.deliveries`).
 
-However often in unit tests, mails will not actually be sent, simply constructed, as in the example above, where the precise content of the email is checked against what it should be.
+This way, emails are not actually sent, simply constructed. The precise content of the email can then be checked against what is expected, as in the example above.
 
 ### Functional Testing
 
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index a7ca531123..03ef770352 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -51,7 +51,7 @@ with an id of `results`.
 
 Rails provides quite a bit of built-in support for building web pages with this
 technique. You rarely have to write this code yourself. The rest of this guide
-will show you how Rails can help you write web sites in this manner, but it's
+will show you how Rails can help you write websites in this way, but it's
 all built on top of this fairly simple technique.
 
 Unobtrusive JavaScript