diff --git a/modules/aggregator/aggregator.module b/modules/aggregator/aggregator.module
index 1e1686a..d1eb204 100644
--- a/modules/aggregator/aggregator.module
+++ b/modules/aggregator/aggregator.module
@@ -761,3 +761,12 @@ function aggregator_sanitize_configuration() {
 function _aggregator_items($count) {
   return format_plural($count, '1 item', '@count items');
 }
+
+/**
+ * Implements hook_preprocess_block().
+ */
+function aggregator_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'aggregator') {
+    $variables['attributes_array']['role'] = 'complementary';
+  }
+}
diff --git a/modules/blog/blog.module b/modules/blog/blog.module
index 731bd2f..b986d58 100644
--- a/modules/blog/blog.module
+++ b/modules/blog/blog.module
@@ -270,3 +270,12 @@ function blog_rdf_mapping() {
     ),
   );
 }
+
+/**
+ * Implements hook_preprocess_block().
+ */
+function blog_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'blog') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
diff --git a/modules/book/book.module b/modules/book/book.module
index de9561f..6478693 100644
--- a/modules/book/book.module
+++ b/modules/book/book.module
@@ -959,6 +959,15 @@ function _book_link_defaults($nid) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function book_preprocess_block(&$variables) {
+  if ($variables['block']-> module == 'book') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
+
+/**
  * Process variables for book-all-books-block.tpl.php.
  *
  * The $variables array contains the following arguments:
diff --git a/modules/comment/comment.module b/modules/comment/comment.module
index 60a9ca4..98cecef 100644
--- a/modules/comment/comment.module
+++ b/modules/comment/comment.module
@@ -2235,6 +2235,15 @@ function comment_form_submit($form, &$form_state) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function comment_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'comment') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
+
+/**
  * Process variables for comment.tpl.php.
  *
  * @see comment.tpl.php
diff --git a/modules/forum/forum.module b/modules/forum/forum.module
index c58b5c9..a360dab 100644
--- a/modules/forum/forum.module
+++ b/modules/forum/forum.module
@@ -959,6 +959,15 @@ function forum_get_topics($tid, $sortby, $forum_per_page) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function forum_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'forum') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
+
+/**
  * Process variables for forums.tpl.php
  *
  * The $variables array contains the following arguments:
diff --git a/modules/help/help.module b/modules/help/help.module
index 773a52d..2bb81a6 100644
--- a/modules/help/help.module
+++ b/modules/help/help.module
@@ -61,3 +61,12 @@ function help_help($path, $arg) {
       return $output;
   }
 }
+
+/**
+ * Implements hook_preprocess_block().
+ */
+function help_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'help') {
+    $variables['attributes_array']['role'] = 'complementary';
+  }
+}
diff --git a/modules/locale/locale.module b/modules/locale/locale.module
index 0788461..fdd86a9 100644
--- a/modules/locale/locale.module
+++ b/modules/locale/locale.module
@@ -1036,3 +1036,12 @@ function locale_form_comment_form_alter(&$form, &$form_state, $form_id) {
     $form['language']['#value'] = $language_content->language;
   }
 }
+
+/**
+ * Implements hook_preprocess_block().
+ */
+function locale_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'locale') {
+    $variables['attributes_array']['role'] = 'complementary';
+  }
+}
diff --git a/modules/menu/menu.module b/modules/menu/menu.module
index fc8f68a..8d36e49 100644
--- a/modules/menu/menu.module
+++ b/modules/menu/menu.module
@@ -760,3 +760,12 @@ function menu_get_menus($all = TRUE) {
   }
   return $custom_menus;
 }
+
+/**
+ * Implements hook_preprocess_block().
+ */
+function menu_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'menu') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
diff --git a/modules/node/node.module b/modules/node/node.module
index 2dd1926..9b4bc00 100644
--- a/modules/node/node.module
+++ b/modules/node/node.module
@@ -1423,6 +1423,23 @@ function node_is_page($node) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function node_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'node') {
+    switch ($variables['block']->delta) {
+      case 'syndicate':
+        $variables['attributes_array']['role'] = 'complementary';
+        break;
+
+      case 'recent':
+        $variables['attributes_array']['role'] = 'navigation';
+        break;
+    }
+  }
+}
+
+/**
  * Process variables for node.tpl.php
  *
  * Most themes utilize their own copy of node.tpl.php. The default is located
diff --git a/modules/poll/poll.module b/modules/poll/poll.module
index f45b8bd..95f4aa0 100644
--- a/modules/poll/poll.module
+++ b/modules/poll/poll.module
@@ -776,6 +776,15 @@ function poll_vote($form, &$form_state) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function poll_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'poll') {
+    $variables['attributes_array']['role'] = 'complementary';
+  }
+}
+
+/**
  * Themes the voting form for a poll.
  *
  * Inputs: $form
diff --git a/modules/profile/profile.module b/modules/profile/profile.module
index 2374fe8..d8cd5ef 100644
--- a/modules/profile/profile.module
+++ b/modules/profile/profile.module
@@ -529,6 +529,15 @@ function profile_category_access($account, $category) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function profile_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'profile') {
+    $variables['attributes_array']['role'] = 'complementary';
+  }
+}
+
+/**
  * Process variables for profile-block.tpl.php.
  *
  * The $variables array contains the following arguments:
diff --git a/modules/search/search.module b/modules/search/search.module
index 518272a..a0dabb4 100644
--- a/modules/search/search.module
+++ b/modules/search/search.module
@@ -1349,3 +1349,11 @@ function search_forms() {
   return $forms;
 }
 
+/**
+ * Implements hook_preprocess_block().
+ */
+function search_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'search') {
+    $variables['attributes_array']['role'] = 'search';
+  }
+}
diff --git a/modules/shortcut/shortcut.module b/modules/shortcut/shortcut.module
index d2ac72b..b2ef56e 100644
--- a/modules/shortcut/shortcut.module
+++ b/modules/shortcut/shortcut.module
@@ -640,6 +640,15 @@ function shortcut_renderable_links($shortcut_set = NULL) {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function shortcut_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'shortcut') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
+
+/**
  * Implements hook_preprocess_page().
  */
 function shortcut_preprocess_page(&$variables) {
diff --git a/modules/statistics/statistics.module b/modules/statistics/statistics.module
index 6b7be8a..4b6f7be 100644
--- a/modules/statistics/statistics.module
+++ b/modules/statistics/statistics.module
@@ -425,3 +425,11 @@ function statistics_ranking() {
 function statistics_update_index() {
   variable_set('node_cron_views_scale', 1.0 / max(1, db_query('SELECT MAX(totalcount) FROM {node_counter}')->fetchField()));
 }
+/**
+ * Implements hook_preprocess_block().
+ */
+function statistics_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'statistics') {
+    $variables['attributes_array']['role'] = 'navigation';
+  }
+}
diff --git a/modules/system/system.module b/modules/system/system.module
index 3ebc657..743a695 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -2066,9 +2066,28 @@ function system_block_view($delta = '') {
  * Implements hook_preprocess_block().
  */
 function system_preprocess_block(&$variables) {
-  // System menu blocks should get the same class as menu module blocks.
-  if ($variables['block']->module == 'system' && in_array($variables['block']->delta, array_keys(menu_list_system_menus()))) {
-    $variables['classes_array'][] = 'block-menu';
+  if ($variables['block']->module == 'system') {
+
+    switch ($variables['block']->delta) {
+      case 'main':
+        $variables['attributes_array']['role'] = 'main';
+        break;
+
+      case 'powered-by':
+        $variables['attributes_array']['role'] = 'complementary';
+        break;
+
+      case 'help':
+        $variables['attributes_array']['role'] = 'complementary';
+        break;
+
+      // System menu blocks should get the same class as menu module blocks.
+      default:
+        if (in_array($variables['block']->delta, array_keys(menu_list_system_menus()))) {
+          $variables['attributes_array']['role'] = 'navigation';
+          $variables['classes_array'][] = 'block-menu';
+        }
+    }
   }
 }
 
diff --git a/modules/user/user.module b/modules/user/user.module
index ffd170c..adb2b59 100644
--- a/modules/user/user.module
+++ b/modules/user/user.module
@@ -1411,6 +1411,27 @@ function user_block_view($delta = '') {
 }
 
 /**
+ * Implements hook_preprocess_block().
+ */
+function user_preprocess_block(&$variables) {
+  if ($variables['block']->module == 'user') {
+    switch ($variables['block']->delta) {
+      case 'login':
+        $variables['attributes_array']['role'] = 'form';
+        break;
+
+      case 'new':
+        $variables['attributes_array']['role'] = 'complementary';
+        break;
+
+      case 'online':
+        $variables['attributes_array']['role'] = 'complementary';
+        break;
+    }
+  }
+}
+
+/**
  * Process variables for user-picture.tpl.php.
  *
  * The $variables array contains the following arguments: