diff --git a/_app/_posts/note/2014-02-01-custom-heading-image.md b/_app/_posts/note/2014-02-01-custom-heading-image.md
index 3b0b176ed..877cdf09f 100644
--- a/_app/_posts/note/2014-02-01-custom-heading-image.md
+++ b/_app/_posts/note/2014-02-01-custom-heading-image.md
@@ -20,7 +20,7 @@ heading-img-width: 400
 `heading-img`
 : Heading image filename, if a relative URL (non-external URL) is provided, the file will be prefixed with `site.file`.
 
-`heading-bg-local`
+`heading-img-local`
 : To avoid relative URL prefixed by `site.file`, you can set this option to `true` to prefix it with `amsf_user_assets`, then you can store your images in `_app/assets/`.
 
 `heading-img-width`
diff --git a/_app/_posts/note/2017-01-06-open-graph.md b/_app/_posts/note/2017-01-06-open-graph.md
index 52fef6943..013fd242d 100644
--- a/_app/_posts/note/2017-01-06-open-graph.md
+++ b/_app/_posts/note/2017-01-06-open-graph.md
@@ -13,6 +13,7 @@ It will look for the image in the following order:
 1. Use `page.thumbnail` if defined in your post [front-matter field](http://jekyllrb.com/docs/frontmatter/).
 2. If no specified `page.thumbnail` defined, it uses [Heading Background Image]({{ site.base }}/custom-heading-background.html) (aka. `page.heading-bg`) if defined in your post front-matter field.
 3. If no heading background image found, Curtana will try to grab the first image (wrapped inside `<img>`) in your post as your post thumbnail
+4. If nothing found, it fails back to `logo.png` located at your site root.
 
 You can always use `page.thumb_force_logo` in your post front-matter field to override the above lookup.