diff --git a/core/modules/system/templates/maintenance-page.html.twig b/core/modules/system/templates/maintenance-page.html.twig
index fd780d4..2700977 100644
--- a/core/modules/system/templates/maintenance-page.html.twig
+++ b/core/modules/system/templates/maintenance-page.html.twig
@@ -11,7 +11,7 @@
  * @ingroup themeable
  */
 #}
-<div class="layout-container">
+<div>
 
   <header role="banner">
     {% if logo %}
@@ -21,15 +21,15 @@
     {% endif %}
 
     {% if site_name or site_slogan %}
-      <div class="name-and-slogan">
+      <div>
         {% if site_name %}
-         <h1 class="site-name">
+         <h1>
            <a href="{{ front_page }}" title="{{ 'Home'|t }}" rel="home">{{ site_name }}</a>
          </h1>
         {% endif %}
 
         {% if site_slogan %}
-          <div class="site-slogan">{{ site_slogan }}</div>
+          <div>{{ site_slogan }}</div>
         {% endif %}
       </div>{# /.name-and-slogan #}
     {% endif %}
@@ -47,13 +47,13 @@
   </main>
 
   {% if page.sidebar_first %}
-    <aside class="layout-sidebar-first" role="complementary">
+    <aside role="complementary">
       {{ page.sidebar_first }}
     </aside>{# /.layout-sidebar-first #}
   {% endif %}
 
   {% if page.sidebar_second %}
-    <aside class="layout-sidebar-second" role="complementary">
+    <aside role="complementary">
       {{ page.sidebar_second }}
     </aside>{# /.layout-sidebar-second #}
   {% endif %}
diff --git a/core/modules/system/templates/maintenance-task-list.html.twig b/core/modules/system/templates/maintenance-task-list.html.twig
index 649cfa6..51ee57a 100644
--- a/core/modules/system/templates/maintenance-task-list.html.twig
+++ b/core/modules/system/templates/maintenance-task-list.html.twig
@@ -15,7 +15,7 @@
  */
 #}
 <h2 class="visually-hidden">Installation tasks</h2>
-<ol class="task-list">
+<ol>
 {% for task in tasks %}
   <li{{ task.attributes }}>
     {{ task.item }}
diff --git a/core/modules/system/templates/mark.html.twig b/core/modules/system/templates/mark.html.twig
index 2798bb0..1697de3 100644
--- a/core/modules/system/templates/mark.html.twig
+++ b/core/modules/system/templates/mark.html.twig
@@ -15,8 +15,8 @@
 #}
 {% if logged_in %}
   {% if status is constant('MARK_NEW') %}
-    <span class="marker">{{ 'new'|t }}</span>
+    <span>{{ 'new'|t }}</span>
   {% elseif status is constant('MARK_UPDATED') %}
-    <span class="marker">{{ 'updated'|t }}</span>
+    <span>{{ 'updated'|t }}</span>
   {% endif %}
 {% endif %}
diff --git a/core/modules/system/templates/menu-local-tasks.html.twig b/core/modules/system/templates/menu-local-tasks.html.twig
index dce922b..3f3a24b 100644
--- a/core/modules/system/templates/menu-local-tasks.html.twig
+++ b/core/modules/system/templates/menu-local-tasks.html.twig
@@ -17,9 +17,9 @@
 #}
 {% if primary %}
   <h2 class="visually-hidden">{{ 'Primary tabs'|t }}</h2>
-  <ul class="tabs primary">{{ primary }}</ul>
+  <ul>{{ primary }}</ul>
 {% endif %}
 {% if secondary %}
   <h2 class="visually-hidden">{{ 'Secondary tabs'|t }}</h2>
-  <ul class="tabs secondary">{{ secondary }}</ul>
+  <ul>{{ secondary }}</ul>
 {% endif %}
diff --git a/core/modules/system/templates/menu.html.twig b/core/modules/system/templates/menu.html.twig
index f01ce84..a9c7899 100644
--- a/core/modules/system/templates/menu.html.twig
+++ b/core/modules/system/templates/menu.html.twig
@@ -27,9 +27,9 @@
   {% import _self as menus %}
   {% if items %}
     {% if menu_level == 0 %}
-      <ul{{ attributes.addClass('menu') }}>
+      <ul{{ attributes }}>
     {% else %}
-      <ul class="menu">
+      <ul>
     {% endif %}
       {% for item in items %}
         <li{{ item.attributes }}>