diff --git a/content/two_column_addons.css b/content/two_column_addons.css
index 05574eb..b3bd8e8 100644
--- a/content/two_column_addons.css
+++ b/content/two_column_addons.css
@@ -2,16 +2,28 @@
 
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 @-moz-document url("about:addons"){
-  #addon-list{
-    display: grid;
-    grid-template-areas: "a a";
-    grid-template-columns: 1fr 1fr;
-		grid-auto-rows: min-content;
+	/* Test for Firefox > 66 */
+	@supports (inset-block:auto){
+    #addon-list{
+      display: grid;
+      grid-template-areas: "a a";
+      grid-template-columns: 1fr 1fr;
+		  grid-auto-rows: min-content;
+    }
+  }
+	/* Test for Firefox < 66 */
+	@supports not (inset-block:auto){
+    #addon-list > scrollbox > .scrollbox-innerbox{
+      display: grid;
+      grid-template-areas: "a a";
+      grid-template-columns: 1fr 1fr;
+      grid-auto-rows: min-content;
+    }
   }
   .control-container{ display: flex; }
   .addon-control{ margin: 3px }
   .addon.card{ padding-bottom: 0px !important; padding-top: 0px !important }
-  .addon.card > .content-container { display: flex;  }
+  .addon.card > .content-container { display: flex; }
   .content-inner-container{ flex-grow: 1; }
   .content-inner-container > hbox{ display: block }
   .icon{ min-width: 24px }