diff --git a/lib/rdoc/generator/template/rails/resources/css/main.css b/lib/rdoc/generator/template/rails/resources/css/main.css
index 2b3bb1d1..1b075a89 100644
--- a/lib/rdoc/generator/template/rails/resources/css/main.css
+++ b/lib/rdoc/generator/template/rails/resources/css/main.css
@@ -23,7 +23,7 @@ body {
   grid-template-columns: 100%;
 }
 
-@media (min-width: 40em) {
+@media (min-width: 600px) {
   body {
     grid-template-rows: min-content min-content auto min-content;
     grid-template-columns: 300px auto;
@@ -238,7 +238,7 @@ pre
   margin: 1em;
 }
 
-@media (min-width: 40em) {
+@media (min-width: 600px) {
   #content {
     max-width: 980px;
     margin: 2em 3.5em;
diff --git a/lib/rdoc/generator/template/rails/resources/css/panel.css b/lib/rdoc/generator/template/rails/resources/css/panel.css
index 3f79bacf..f9aab79f 100644
--- a/lib/rdoc/generator/template/rails/resources/css/panel.css
+++ b/lib/rdoc/generator/template/rails/resources/css/panel.css
@@ -4,7 +4,7 @@
         display: none;
     }
 
-    @media (max-width: 39.99em) {
+    @media (max-width: 599px) {
         .panel_mobile_button {
             display: block;
             height: 40px;
@@ -90,7 +90,7 @@
         line-height: 1;
     }
 
-    @media (max-width: 39.99em) {
+    @media (max-width: 599px) {
         .panel
         {
             transition: left 0s ease-in-out;
@@ -122,7 +122,7 @@
       text-align: center;
     }
 
-    @media (max-width: 39.99em) {
+    @media (max-width: 599px) {
       .panel .logo img {
         width: 50%;
       }
@@ -143,7 +143,7 @@
             overflow-x: hidden;
         }
 
-        @media (max-width: 39.99em) {
+        @media (max-width: 599px) {
             .panel .header
             {
                 width: 100%;
@@ -164,7 +164,7 @@
             outline: none;
         }
 
-        @media (max-width: 39.99em) {
+        @media (max-width: 599px) {
             .panel .header input
             {
                 width: 70%;