diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 798bc05..9a130ab 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -96,6 +96,11 @@
 ColumnLimit:     80
 ```
 
+### HTML/CSS
+
+We follow the
+[Google HTML/CSS Style Guide](https://google.github.io/styleguide/htmlcssguide.html).
+
 ### C
 
 For C code, we typically use the Linux coding style, which is documented at: