diff --git a/doc/js/gfm-mod.css b/doc/css/gfm-mod.css
similarity index 99%
rename from doc/js/gfm-mod.css
rename to doc/css/gfm-mod.css
index c2d11b6612..5cd333d7a9 100644
--- a/doc/js/gfm-mod.css
+++ b/doc/css/gfm-mod.css
@@ -1060,9 +1060,8 @@ div#sidebar {
   float: left;
   position: sticky;
   top: 5px;
-  width: 200px;
-  max-width: 200px;
-  font-size: 85%;
+  min-width: 200px;
+  font-size: 90%;
 }
 
 div#sidebar ul {
@@ -1103,11 +1102,11 @@ div#sidebar details summary::-webkit-details-marker {
 }
 
 div#sidebar details summary::after {
-  content: " ►";
+  content: " [+]";
 }
 
 div#sidebar details[open] summary::after {
-  content: " ▼";
+  content: " [-]";
 }
 
 @media screen and (max-width: 1140px) {
@@ -1120,4 +1119,8 @@ div#sidebar details[open] summary::after {
   div#content {
     margin-left: 200px;
   }
+
+  div#sidebar {
+    max-width: 200px;
+  }
 }
diff --git a/doc/js/rouge-github-mod.css b/doc/css/rouge-github-mod.css
similarity index 100%
rename from doc/js/rouge-github-mod.css
rename to doc/css/rouge-github-mod.css
diff --git a/scripts/build-docs.sh b/scripts/build-docs.sh
index 168431c87b..49b6360164 100755
--- a/scripts/build-docs.sh
+++ b/scripts/build-docs.sh
@@ -285,7 +285,7 @@ create_page_sidebar_section()
 
 rm -rf "$output_dir";
 mkdir -p "$output_dir";
-cp doc/js/* "$output_dir";
+cp doc/css/* "$output_dir";
 mkdir -p "$output_dir/user/img/";
 cp doc/img/* "$output_dir/user/img/";
 mkdir -p "$output_dir/tutorials/res/";