diff --git a/guides/source/api_documentation_guidelines.md b/guides/source/api_documentation_guidelines.md
index f3e869dd26..386a0328f1 100644
--- a/guides/source/api_documentation_guidelines.md
+++ b/guides/source/api_documentation_guidelines.md
@@ -263,6 +263,8 @@ Use fixed-width fonts for:
 * Symbols
 * Method parameters
 * File names
+* HTML tags and attributes
+* CSS selectors, attributes and values
 
 ```ruby
 class Array