5 files changed, 36 insertions, 10 deletions
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 45e9b77eea..3b926c04f0 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -270,7 +270,7 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 *   Changed the `protect_from_forgery` prepend default to `false`.
     ([commit](https://github.com/rails/rails/commit/39794037817703575c35a75f1961b01b83791191))
 
-*   `ActionController::TestCase` will be moved to it's own gem in Rails 5.1. Use
+*   `ActionController::TestCase` will be moved to its own gem in Rails 5.1. Use
     `ActionDispatch::IntegrationTest` instead.
     ([commit](https://github.com/rails/rails/commit/4414c5d1795e815b102571425974a8b1d46d932d))
 
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index d49df23e4a..0e6bb76101 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -1419,7 +1419,7 @@ number_to_percentage(100, precision: 0)        # => 100%
 
 #### number_to_phone
 
-Formats a number into a US phone number.
+Formats a number into a phone number (US by default).
 
 ```ruby
 number_to_phone(1235551234) # => 123-555-1234
diff --git a/guides/source/active_model_basics.md b/guides/source/active_model_basics.md
index a8199e5d02..e834aeadb1 100644
--- a/guides/source/active_model_basics.md
+++ b/guides/source/active_model_basics.md
@@ -13,7 +13,7 @@ After reading this guide, you will know:
 * How an Active Record model behaves.
 * How Callbacks and validations work.
 * How serializers work.
-* The Rails internationalization (i18n) framework.
+* How Active Model integrates with the Rails internationalization (i18n) framework.
 
 --------------------------------------------------------------------------------
 
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index bd16ccad12..1cf4abce10 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -785,7 +785,7 @@ A `String` `:message` value can optionally contain any/all of `%{value}`,
 `%{attribute}`, and `%{model}` which will be dynamically replaced when
 validation fails.
 
-A `Proc` `:message` value is given two arguments: a message key for i18n, and
+A `Proc` `:message` value is given two arguments: the object being validated, and
 a hash with `:model`, `:attribute`, and `:value` key-value pairs.
 
 ```ruby
@@ -801,10 +801,10 @@ class Person < ApplicationRecord
   # Proc
   validates :username,
     uniqueness: {
-      # key = "activerecord.errors.models.person.attributes.username.taken"
+      # object = person object being validated
       # data = { model: "Person", attribute: "Username", value: <username> }
-      message: ->(key, data) do
-        "#{data[:value]} taken! Try again #{Time.zone.tomorrow}"
+      message: ->(object, data) do
+        "Hey #{object.name}!, #{data[:value]} is taken already! Try again #{Time.zone.tomorrow}"
       end
     }
 end
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index ec4444eb43..ae204a55d6 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -512,12 +512,38 @@ class ProductsController < ApplicationController
 end
 ```
 
-### A note on weak ETags
+### Strong v/s Weak ETags
 
-Etags generated by Rails are weak by default. Weak etags allow semantically equivalent responses to have the same etags, even if their bodies do not match exactly. This is useful when we don't want the page to be regenerated for minor changes in response body. If you absolutely need to generate a strong etag, it can be assigned to the header directly.
+Rails generates weak ETags by default. Weak ETags allow semantically equivalent
+responses to have the same ETags, even if their bodies do not match exactly.
+This is useful when we don't want the page to be regenerated for minor changes in
+response body.
+
+Weak ETags have a leading `W/` to differentiate them from strong ETags.
+
+```
+  W/"618bbc92e2d35ea1945008b42799b0e7" → Weak ETag
+  "618bbc92e2d35ea1945008b42799b0e7" → Strong ETag
+```
+
+Unlike weak ETag, Strong ETag implies that response should be exactly same
+and byte by byte identical. Useful when doing Range requests within a
+large video or PDF file. Some CDNs support only strong ETags, like Akamai.
+If you absolutely need to generate a strong ETag, it can be done as follows.
+
+```ruby
+  class ProductsController < ApplicationController
+    def show
+      @product = Product.find(params[:id])
+      fresh_when last_modified: @product.published_at.utc, strong_etag: @product
+    end
+  end
+```
+
+You can also set the strong ETag directly on the response.
 
 ```ruby
-  response.add_header "ETag", Digest::MD5.hexdigest(response.body)
+  response.strong_etag = response.body # => "618bbc92e2d35ea1945008b42799b0e7"
 ```
 
 References