diff --git a/app/models/user.rb b/app/models/user.rb
index a97b37df..46adacff 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -29,11 +29,11 @@ class User < ActiveRecord::Base
   SCREEN_NAME_REGEX = /\A[a-zA-Z0-9_]{1,16}\z/
   WEBSITE_REGEX = /https?:\/\/([A-Za-z.\-]+)\/?(?:.*)/i
 
-  validates :screen_name, presence: true, format: { with: SCREEN_NAME_REGEX }, uniqueness: { case_sensitive: false }#,
-            #exclusion: { in: %w(justask_admin retrospring_admin admin justask retrospring support about public
-            #                    notifications inbox sign_in sign_up sidekiq moderation moderator mod administrator
-            #                    siteadmin site_admin),
-            #             message: "%{value} is reserved." }
+  before_validation do
+    screen_name.strip!
+  end
+
+  validates :screen_name, presence: true, format: { with: SCREEN_NAME_REGEX }, uniqueness: { case_sensitive: false }, screen_name: true
 
   validates :display_name, length: { maximum: 50 }
   validates :bio, length: { maximum: 200 }
diff --git a/app/validators/screen_name_validator.rb b/app/validators/screen_name_validator.rb
new file mode 100644
index 00000000..e0158662
--- /dev/null
+++ b/app/validators/screen_name_validator.rb
@@ -0,0 +1,11 @@
+class ScreenNameValidator < ActiveModel::EachValidator
+  FORBIDDEN_SCREEN_NAMES = %w(justask_admin retrospring_admin admin justask retrospring support about public
+                              notifications inbox sign_in sign_up sidekiq moderation moderator mod administrator
+                              siteadmin site_admin help retro_spring retroospring retrosprlng niisding nllsding)
+
+  def validate_each(record, attribute, value)
+    if FORBIDDEN_SCREEN_NAMES.include? value.downcase
+      record.errors[attribute] << "Thou shalt not use this username!  Please choose another one."
+    end
+  end
+end
\ No newline at end of file
diff --git a/app/views/static/about.html.haml b/app/views/static/about.html.haml
index c814733f..b2ad025e 100644
--- a/app/views/static/about.html.haml
+++ b/app/views/static/about.html.haml
@@ -107,6 +107,6 @@
           %ul.about--moderator
             - User.where(supporter: true).each do |sup|
               %a{href: show_user_profile_path(sup.screen_name), title: sup.screen_name, data: { toggle: :tooltip, placement: :top }}
-                %img.img-rounded.answerbox--img-small{src: sup.profile_picture_url(:medium)}
+                %img.img-rounded.answerbox--img-small{src: sup.profile_picture.url(:medium)}
 
 = render "shared/links"
diff --git a/config/application.rb b/config/application.rb
index 21270043..e30ee771 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -19,5 +19,6 @@ module Justask
     # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
     # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
     # config.i18n.default_locale = :de
+    config.autoload_paths += %W["#{config.root}/app/validators"]
   end
 end