diff --git a/Doc/tools/sphinxext/static/basic.css b/Doc/tools/sphinxext/static/basic.css
--- a/Doc/tools/sphinxext/static/basic.css
+++ b/Doc/tools/sphinxext/static/basic.css
@@ -40,13 +40,16 @@
 div.sphinxsidebarwrapper {
     padding: 10px 5px 0 10px;
     word-wrap: break-word;
+    height: 100%;
+    overflow: auto;
 }
 
 div.sphinxsidebar {
     float: left;
     width: 230px;
-    margin-left: -100%;
     font-size: 90%;
+    position: fixed;
+    height: 100%;
 }
 
 div.sphinxsidebar ul {