Changes as suggested.

Author: digi-booster

images/image-set-type.html

@@ -16,7 +16,7 @@
 
     <style class="editable">
        .box {
-           background-image: -webkit-image-set(
+          background-image: -webkit-image-set(
             url("large-balloons.avif") type("image/avif"),
             url("large-balloons.jpg") type("image/jpeg"));
           background-image: image-set(
@@ -33,6 +33,9 @@
 
     <textarea class="playable playable-css" style="height: 150px;">
 .box {
+  background-image: -webkit-image-set(
+    url("large-balloons.avif") type("image/avif"),
+    url("large-balloons.jpg") type("image/jpeg"));
   background-image: image-set(
     url("large-balloons.avif") type("image/avif"),
     url("large-balloons.jpg") type("image/jpeg"));