Document default trim mode for Erubis and affected ERB tags [ci skip]

Fixes #12963

1 files changed, 1 insertions, 1 deletions

diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 5e0010725e..669086edbe 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -378,7 +378,7 @@ encrypted cookies salt value. Defaults to `'signed encrypted cookie'`.
 
 * `config.action_view.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action View. Set to `nil` to disable logging.
 
-* `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.erb_trim_mode` gives the trim mode to be used by ERB. It defaults to `'-'`, which turns on trimming of tail spaces and newline when using `<%= -%>` or `<%= =%>`. See the [Erubis documentation](http://www.kuwata-lab.com/erubis/users-guide.06.html#topics-trimspaces) for more information.
 
 * `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`