diff --git a/application/config/ConfigManager.php b/application/config/ConfigManager.php
index e45bb4c3..4c98be30 100644
--- a/application/config/ConfigManager.php
+++ b/application/config/ConfigManager.php
@@ -3,6 +3,7 @@
 
 use Shaarli\Config\Exception\MissingFieldConfigException;
 use Shaarli\Config\Exception\UnauthorizedConfigException;
+use Shaarli\Thumbnailer;
 
 /**
  * Class ConfigManager
@@ -361,7 +362,7 @@ protected function setDefaultValues()
         $this->setEmpty('security.open_shaarli', false);
         $this->setEmpty('security.allowed_protocols', ['ftp', 'ftps', 'magnet']);
 
-        $this->setEmpty('general.header_link', '?');
+        $this->setEmpty('general.header_link', '/');
         $this->setEmpty('general.links_per_page', 20);
         $this->setEmpty('general.enabled_plugins', self::$DEFAULT_PLUGINS);
         $this->setEmpty('general.default_note_title', 'Note: ');
@@ -381,6 +382,7 @@ protected function setDefaultValues()
         // default state of the 'remember me' checkbox of the login form
         $this->setEmpty('privacy.remember_user_default', true);
 
+        $this->setEmpty('thumbnails.mode', Thumbnailer::MODE_ALL);
         $this->setEmpty('thumbnails.width', '125');
         $this->setEmpty('thumbnails.height', '90');
 
diff --git a/application/container/ContainerBuilder.php b/application/container/ContainerBuilder.php
index 593aafb7..bfe93501 100644
--- a/application/container/ContainerBuilder.php
+++ b/application/container/ContainerBuilder.php
@@ -99,7 +99,6 @@ public function build(): ShaarliContainer
         $container['pluginManager'] = function (ShaarliContainer $container): PluginManager {
             $pluginManager = new PluginManager($container->conf);
 
-            // FIXME! Configuration is already injected
             $pluginManager->load($container->conf->get('general.enabled_plugins'));
 
             return $pluginManager;
diff --git a/application/front/ShaarliMiddleware.php b/application/front/ShaarliMiddleware.php
index e9f5552d..fd978e99 100644
--- a/application/front/ShaarliMiddleware.php
+++ b/application/front/ShaarliMiddleware.php
@@ -56,7 +56,7 @@ public function __invoke(Request $request, Response $response, callable $next):
         } catch (ShaarliFrontException $e) {
             // Possible functional error
             $this->container->pageBuilder->reset();
-            $this->container->pageBuilder->assign('message', $e->getMessage());
+            $this->container->pageBuilder->assign('message', nl2br($e->getMessage()));
 
             $response = $response->withStatus($e->getCode());
 
diff --git a/application/front/controller/admin/ConfigureController.php b/application/front/controller/admin/ConfigureController.php
index 865fc2b0..e675fcca 100644
--- a/application/front/controller/admin/ConfigureController.php
+++ b/application/front/controller/admin/ConfigureController.php
@@ -98,10 +98,10 @@ public function save(Request $request, Response $response): Response
         if ($thumbnailsMode !== Thumbnailer::MODE_NONE
             && $thumbnailsMode !== $this->container->conf->get('thumbnails.mode', Thumbnailer::MODE_NONE)
         ) {
-            $this->saveWarningMessage(t(
-                'You have enabled or changed thumbnails mode. '
-                .'<a href="'. $this->container->basePath .'/admin/thumbnails">Please synchronize them</a>.'
-            ));
+            $this->saveWarningMessage(
+                t('You have enabled or changed thumbnails mode.') .
+                '<a href="'. $this->container->basePath .'/admin/thumbnails">' . t('Please synchronize them.') .'</a>'
+            );
         }
         $this->container->conf->set('thumbnails.mode', $thumbnailsMode);
 
@@ -110,8 +110,13 @@ public function save(Request $request, Response $response): Response
             $this->container->history->updateSettings();
             $this->container->pageCacheManager->invalidateCaches();
         } catch (Throwable $e) {
-            // TODO: translation + stacktrace
-            $this->saveErrorMessage('ERROR while writing config file after configuration update.');
+            $this->assignView('message', t('Error while writing config file after configuration update.'));
+
+            if ($this->container->conf->get('dev.debug', false)) {
+                $this->assignView('stacktrace', $e->getMessage() . PHP_EOL . $e->getTraceAsString());
+            }
+
+            return $response->write($this->render('error'));
         }
 
         $this->saveSuccessMessage(t('Configuration was saved.'));
diff --git a/application/front/controller/visitor/InstallController.php b/application/front/controller/visitor/InstallController.php
index aa032860..94ebb4ae 100644
--- a/application/front/controller/visitor/InstallController.php
+++ b/application/front/controller/visitor/InstallController.php
@@ -128,13 +128,14 @@ public function save(Request $request, Response $response): Response
                 $this->container->conf->get('credentials.salt')
             )
         );
+        $this->container->conf->set('general.header_link', $this->container->basePath);
 
         try {
             // Everything is ok, let's create config file.
             $this->container->conf->write($this->container->loginManager->isLoggedIn());
         } catch (\Exception $e) {
-            $this->assignView('message', $e->getMessage());
-            $this->assignView('stacktrace', $e->getTraceAsString());
+            $this->assignView('message', t('Error while writing config file after configuration update.'));
+            $this->assignView('stacktrace', $e->getMessage() . PHP_EOL . $e->getTraceAsString());
 
             return $response->write($this->render('error'));
         }
@@ -155,18 +156,14 @@ protected function checkPermissions(): bool
     {
         // Ensure Shaarli has proper access to its resources
         $errors = ApplicationUtils::checkResourcePermissions($this->container->conf);
-
         if (empty($errors)) {
             return true;
         }
 
-        // FIXME! Do not insert HTML here.
-        $message = '<p>'. t('Insufficient permissions:') .'</p><ul>';
-
+        $message = t('Insufficient permissions:') . PHP_EOL;
         foreach ($errors as $error) {
-            $message .= '<li>'.$error.'</li>';
+            $message .= PHP_EOL . $error;
         }
-        $message .= '</ul>';
 
         throw new ResourcePermissionException($message);
     }
diff --git a/application/front/controller/visitor/TagController.php b/application/front/controller/visitor/TagController.php
index c176f43f..de4e7ea2 100644
--- a/application/front/controller/visitor/TagController.php
+++ b/application/front/controller/visitor/TagController.php
@@ -11,8 +11,6 @@
  * Class TagController
  *
  * Slim controller handle tags.
- *
- * TODO: check redirections with new helper
  */
 class TagController extends ShaarliVisitorController
 {
diff --git a/application/legacy/LegacyUpdater.php b/application/legacy/LegacyUpdater.php
index cbf6890f..0ab3a55b 100644
--- a/application/legacy/LegacyUpdater.php
+++ b/application/legacy/LegacyUpdater.php
@@ -534,7 +534,8 @@ public function updateMethodWebThumbnailer()
 
         if ($thumbnailsEnabled) {
             $this->session['warnings'][] = t(
-                'You have enabled or changed thumbnails mode. <a href="./admin/thumbnails">Please synchronize them</a>.'
+                t('You have enabled or changed thumbnails mode.') .
+                '<a href="./admin/thumbnails">' . t('Please synchronize them.') . '</a>'
             );
         }
 
diff --git a/index.php b/index.php
index 42b853a4..26e8da8e 100644
--- a/index.php
+++ b/index.php
@@ -28,7 +28,6 @@
 use Shaarli\Config\ConfigManager;
 use Shaarli\Container\ContainerBuilder;
 use Shaarli\Languages;
-use Shaarli\Plugin\PluginManager;
 use Shaarli\Security\CookieManager;
 use Shaarli\Security\LoginManager;
 use Shaarli\Security\SessionManager;
@@ -65,9 +64,6 @@
 RainTPL::$tpl_dir = $conf->get('resource.raintpl_tpl').'/'.$conf->get('resource.theme').'/'; // template directory
 RainTPL::$cache_dir = $conf->get('resource.raintpl_tmp'); // cache directory
 
-$pluginManager = new PluginManager($conf);
-$pluginManager->load($conf->get('general.enabled_plugins'));
-
 date_default_timezone_set($conf->get('general.timezone', 'UTC'));
 
 $loginManager->checkLoginState(client_ip_id($_SERVER));
diff --git a/tests/front/controller/admin/PluginsControllerTest.php b/tests/front/controller/admin/PluginsControllerTest.php
index 700a0df2..ad0cda70 100644
--- a/tests/front/controller/admin/PluginsControllerTest.php
+++ b/tests/front/controller/admin/PluginsControllerTest.php
@@ -162,7 +162,7 @@ public function testSaveWithError(): void
             ->method('setSessionParameter')
             ->with(
                 SessionManager::KEY_ERROR_MESSAGES,
-                ['ERROR while saving plugin configuration: ' . PHP_EOL . $message]
+                ['Error while saving plugin configuration: ' . PHP_EOL . $message]
             )
         ;
 
diff --git a/tests/front/controller/visitor/InstallControllerTest.php b/tests/front/controller/visitor/InstallControllerTest.php
index 6871fdd9..29c4d7a0 100644
--- a/tests/front/controller/visitor/InstallControllerTest.php
+++ b/tests/front/controller/visitor/InstallControllerTest.php
@@ -189,6 +189,7 @@ public function testSaveInstallValid(): void
             'updates.check_updates' => true,
             'api.enabled' => true,
             'api.secret' => '_NOT_EMPTY',
+            'general.header_link' => '/subfolder',
         ];
 
         $request = $this->createMock(Request::class);
diff --git a/tpl/default/picwall.html b/tpl/default/picwall.html
index 3b5fccc3..b7a56c89 100644
--- a/tpl/default/picwall.html
+++ b/tpl/default/picwall.html
@@ -9,7 +9,8 @@
 {if="count($linksToDisplay)===0 && $is_logged_in"}
   <div class="pure-g pure-alert pure-alert-warning page-single-alert">
     <div class="pure-u-1 center">
-      {'There is no cached thumbnail. Try to <a href="{$base_path}/admin/thumbnails">synchronize them</a>.'|t}
+      {'There is no cached thumbnail.'|t}
+      <a href="{$base_path}/admin/thumbnails">{'Try to synchronize them.'|t}</a>
     </div>
   </div>
 {/if}