diff --git a/frontends/ycdl_flask/static/css/common.css b/frontends/ycdl_flask/static/css/common.css
index bd32129..8ac5554 100644
--- a/frontends/ycdl_flask/static/css/common.css
+++ b/frontends/ycdl_flask/static/css/common.css
@@ -1,3 +1,7 @@
+/*
+These properties are used by javascript functions.
+getComputedStyle(document.documentElement).getPropertyValue("--narrow").trim() === "1"
+*/
 @media screen and (min-width: 800px)
 {
     :root
@@ -5,7 +9,6 @@
         --wide: 1;
     }
 }
-
 @media screen and (max-width: 800px)
 {
     :root