diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index e7ec8df..cee9a58 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1677,27 +1677,29 @@ function template_preprocess_html(&$variables) {
   $variables['page'] = $page;
 
   // Compile a list of classes that are going to be applied to the body element.
-  // This allows advanced theming based on context (home page, node of certain type, etc.).
+  // This allows advanced theming based on context (home page, node of certain
+  // type, etc.).
   $body_classes = $variables['attributes']['class'];
-  $body_classes[] = 'html';
-  // Add a class that tells us whether we're on the front page or not.
-  $body_classes[] = $variables['is_front'] ? 'front' : 'not-front';
-  // Add a class that tells us whether the page is viewed by an authenticated user or not.
-  $body_classes[] = $variables['logged_in'] ? 'logged-in' : 'not-logged-in';
-  $variables['attributes']['class'] = $body_classes;
 
-  $path_args = explode('/', current_path());
-  // Populate the body classes.
-  if ($suggestions = theme_get_suggestions($path_args, 'page', '-')) {
-    foreach ($suggestions as $suggestion) {
-      if ($suggestion != 'page-front') {
-        // Add current suggestion to page classes to make it possible to theme
-        // the page depending on the current page type (e.g. node, admin, user,
-        // etc.) as well as more specific data like node-12 or node-edit.
-        $variables['attributes']['class'][] = drupal_html_class($suggestion);
-      }
-    }
+  // Add a class that tells us whether the page is viewed by an authenticated
+  // user.
+  if ($variables['logged_in']) {
+    $body_classes[] = 'user-logged-in';
   }
+  // Add a class that tells us what path the page is located make it possible
+  // to theme the page depending on the current path (e.g. node, admin, user,
+  // etc.) as well as more specific data like path-frontpage.
+  $path = \Drupal::request()->getPathInfo();
+
+  if (drupal_is_front_page()) {
+    $body_classes[] = 'path-frontpage';
+  }
+  else {
+    $segment = explode('/', $path);
+    $body_classes[] = 'path-' . drupal_html_class($segment[1]);
+  }
+
+  $variables['attributes']['class'] = $body_classes;
 
   $site_config = \Drupal::config('system.site');
   // Construct page title.
@@ -1787,15 +1789,6 @@ function template_preprocess_page(&$variables) {
     }
   }
 
-  // Set up layout variable.
-  $variables['layout'] = 'none';
-  if (!empty($variables['page']['sidebar_first'])) {
-    $variables['layout'] = 'first';
-  }
-  if (!empty($variables['page']['sidebar_second'])) {
-    $variables['layout'] = ($variables['layout'] == 'first') ? 'both' : 'second';
-  }
-
   $variables['base_path']         = base_path();
   $variables['front_page']        = \Drupal::url('<front>');
   $variables['language']          = $language_interface;
@@ -1887,16 +1880,16 @@ function template_preprocess_page(&$variables) {
  */
 function theme_get_suggestions($args, $base, $delimiter = '__') {
 
-  // Build a list of suggested theme hooks or body classes in order of
+  // Build a list of suggested theme hooks in order of
   // specificity. One suggestion is made for every element of the current path,
   // though numeric elements are not carried to subsequent suggestions. For
   // example, for $base='page', http://www.example.com/node/1/edit would result
-  // in the following suggestions and body classes:
+  // in the following suggestions:
   //
-  // page__node              page-node
-  // page__node__%           page-node-%
-  // page__node__1           page-node-1
-  // page__node__edit        page-node-edit
+  // page__node
+  // page__node__%
+  // page__node__1
+  // page__node__edit
 
   $suggestions = array();
   $prefix = $base;
@@ -1951,7 +1944,6 @@ function template_preprocess_maintenance_page(&$variables) {
   $attributes = $page_object->getBodyAttributes();
   $classes = $attributes['class'];
   $classes[] = 'maintenance-page';
-  $classes[] = 'in-maintenance';
   if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
     $classes[] = 'db-offline';
   }
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index bcf5501..5001e1e 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -83,7 +83,7 @@ function block_page_build(&$page) {
     // Append region description if we are rendering the regions demo page.
     $visible_regions = array_keys(system_region_list($theme, REGIONS_VISIBLE));
     foreach ($visible_regions as $region) {
-      $description = '<div class="block-region">' . $all_regions[$region] . '</div>';
+      $description = '<div class="block-region demo-block">' . $all_regions[$region] . '</div>';
       $page[$region]['block_description'] = array(
         '#markup' => $description,
         '#weight' => 15,
diff --git a/core/themes/bartik/css/style.css b/core/themes/bartik/css/style.css
index bce8f71..6e4f95f 100644
--- a/core/themes/bartik/css/style.css
+++ b/core/themes/bartik/css/style.css
@@ -1796,14 +1796,18 @@ div.add-or-remove-shortcuts {
 }
 
 /* ---------- Admin-specific Theming ---------- */
-
 .page-admin #content img {
   margin-right: 15px; /* LTR */
 }
 .page-admin #content .simpletest-image img {
   margin: 0;
 }
-.page-admin-structure-block-demo .block-region {
+.page-admin #admin-dblog img {
+  margin: 0 5px;
+}
+
+/* Block demo mode */
+.demo-block {
   background: #ffff66;
   border: 1px dotted #9f9e00;
   color: #000;
@@ -1813,15 +1817,12 @@ div.add-or-remove-shortcuts {
   text-align: center;
   text-shadow: none;
 }
-.page-admin-structure-block-demo #featured .block-region {
+#featured .demo-block {
   font-size: 0.55em;
 }
-.page-admin-structure-block-demo #header .block-region {
+#header .demo-block {
   width: 500px;
 }
-.page-admin #admin-dblog img {
-  margin: 0 5px;
-}
 
 /* Configuration. */
 div.admin .right,
diff --git a/core/themes/seven/css/layout/node-add.css b/core/themes/seven/css/layout/node-add.css
index 6bbe892..dc2b105 100644
--- a/core/themes/seven/css/layout/node-add.css
+++ b/core/themes/seven/css/layout/node-add.css
@@ -10,12 +10,6 @@
 @media
   screen and (min-width: 780px),
   (orientation: landscape) and (min-device-height: 780px) {
-
-  [class*="page-node-add-"] .messages,
-  .page-node-edit .messages {
-    margin-top: 1em;
-    margin-bottom: 1em;
-  }
 }
 @media
   screen and (max-width: 1020px),
diff --git a/core/themes/seven/css/theme/install-page.css b/core/themes/seven/css/theme/install-page.css
index d114dac..c9d124d 100644
--- a/core/themes/seven/css/theme/install-page.css
+++ b/core/themes/seven/css/theme/install-page.css
@@ -3,7 +3,7 @@
  * Installation styling.
  *
  * Unfortunately we have to make our styling quite strong, to override the
- * .in-maintenance styling.
+ * .maintenance-page styling.
  */
 .install-background {
   background-color: #1275b2;
diff --git a/core/themes/seven/css/theme/maintenance-page.css b/core/themes/seven/css/theme/maintenance-page.css
index 80b18f9..edf9018 100644
--- a/core/themes/seven/css/theme/maintenance-page.css
+++ b/core/themes/seven/css/theme/maintenance-page.css
@@ -13,7 +13,7 @@
 
 /* Maintenance theming */
 .install-page,
-.in-maintenance {
+.maintenance-page {
   background: none;
 }
 .page-title {
@@ -131,13 +131,13 @@
   html {
     display: table;
   }
-  .in-maintenance,
-  .install-page {
+  .install-page,
+  .maintenance-page {
     display: table-cell;
     padding: 1em 0;
     vertical-align: middle;
   }
-  html, .install-page, .in-maintenance {
+  html, .install-page, .maintenance-page {
     margin: 0;
     width: 100%;
     height: 100%;