Fix broken and duplicate headings

guides/source/active_record_validations_callbacks.md

@@ -899,7 +899,7 @@ If you submit the form with empty fields, the result will be similar to the one
 
 ![Error messages](images/error_messages.png)
 
-NOTE: The appearance of the generated HTML will be different from the one shown, unless you have used scaffolding. See [Customizing the Error Messages CSS](#customizing-error-messages-css).
+NOTE: The appearance of the generated HTML will be different from the one shown, unless you have used scaffolding. See [Customizing the Error Messages CSS](#customizing-the-error-messages-css).
 
 You can also use the `error_messages_for` helper to display the error messages of a model assigned to a view template. It is very similar to the previous example and will achieve exactly the same result.
 

guides/source/association_basics.md

@@ -1022,7 +1022,7 @@ The `:source_type` option specifies the source association type for a `has_one :
 
 ##### `:through`
 
-The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail <a href="#the-has_one-through-association">earlier in this guide</a>.
+The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail <a href="#the-has-one-through-association">earlier in this guide</a>.
 
 ##### `:validate`
 
@@ -1367,7 +1367,7 @@ The `:source_type` option specifies the source association type for a `has_many
 
 ##### `:through`
 
-The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed <a href="#the-has_many-through-association">earlier in this guide</a>.
+The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed <a href="#the-has-many-through-association">earlier in this guide</a>.
 
 ##### `:validate`
 

guides/source/command_line.md

@@ -56,7 +56,7 @@ Rails will set you up with what seems like a huge amount of stuff for such a tin
 
 The `rails server` command launches a small web server named WEBrick which comes bundled with Ruby. You'll use this any time you want to access your application through a web browser.
 
-INFO: WEBrick isn't your only option for serving Rails. We'll get to that [later](#different-servers).
+INFO: WEBrick isn't your only option for serving Rails. We'll get to that [later](#server-with-different-backends).
 
 With no further work, `rails server` will run our new shiny Rails app:
 

guides/source/engines.md

@@ -1,4 +1,4 @@
-Getting Started with Engines
+etting Started with Engines
 ============================
 
 In this guide you will learn about engines and how they can be used to provide additional functionality to their host applications through a clean and very easy-to-use interface. You will learn the following things in this guide:
@@ -191,7 +191,7 @@ Blorgh::Engine.routes.draw do
 end
 ```
 
-Note here that the routes are drawn upon the `Blorgh::Engine` object rather than the `YourApp::Application` class. This is so that the engine routes are confined to the engine itself and can be mounted at a specific point as shown in the [test directory](#test-directory section). This is also what causes the engine's routes to be isolated from those routes that are within the application. This is discussed further in the [Routes](#routes) section of this guide.
+Note here that the routes are drawn upon the `Blorgh::Engine` object rather than the `YourApp::Application` class. This is so that the engine routes are confined to the engine itself and can be mounted at a specific point as shown in the [test directory](#test-directory) section. This is also what causes the engine's routes to be isolated from those routes that are within the application. This is discussed further in the [Routes](#routes) section of this guide.
 
 Next, the `scaffold_controller` generator is invoked, generating a controller called `Blorgh::PostsController` (at `app/controllers/blorgh/posts_controller.rb`) and its related views at `app/views/blorgh/posts`. This generator also generates a functional test for the controller (`test/functional/blorgh/posts_controller_test.rb`) and a helper (`app/helpers/blorgh/posts_controller.rb`).
 

guides/source/layouts_and_rendering.md

@@ -1189,7 +1189,7 @@ You can also specify a second partial to be rendered between instances of the ma
 
 Rails will render the `_product_ruler` partial (with no data passed in to it) between each pair of `_product` partials.
 
-#### Partial Layouts
+#### Collection Partial Layouts
 
 When rendering collections it is also possible to use the `:layout` option: