css for marking as unread, and hook for notification page to be part of it when called.

app/views/notifications/index.html.haml

@@ -2,6 +2,7 @@
 -self.extend AspectsHelper
 -self.extend ApplicationHelper
 -self.extend ErrorMessagesHelper
+#notifications_content
   .span-13
     %h2
       %span.notification_count{:class => ('unread' if @notification_count > 0)}
@@ -9,7 +10,6 @@
       = t('.notifications')
   .span-8.last
     = link_to t('.mark_all_as_read'), read_all_notifications_path, :class => 'button'
-
   .span-24.last
     .stream.notifications
       - group_days.each do |day, notes|
@@ -21,7 +21,7 @@
 
           .span-8.notifications_for_day
             - notes.each do |note|
-            .stream_element{:data=>{:guid => note.id}, :class => "#{note.unread ? 'unread' : ''}"}
+              .stream_element{:data=>{:guid => note.id}, :class => "#{note.unread ? 'unread' : 'read'}"}
                 - if note.type == "Notifications::StartedSharing" && contact = current_user.contact_for(note[:target])
                   .right
                     = aspect_membership_dropdown(contact, note[:target], 'left')
@@ -30,5 +30,12 @@
                   = notification_message_for(note)
                 %br
                 %time= timeago(note.created_at)
+                %a{:class => 'unread-setter'}
+                  mark unread
           .span-13.last
       = will_paginate notifications
+
+:javascript
+  $(document).ready(function(){
+    Diaspora.page.header.notifications.setUpNotificationPage( $("#notifications_content" ) );
+  });

public/stylesheets/sass/application.sass

@@ -2987,6 +2987,12 @@ ul.left_nav
   .user_card
     :margin-left 8px
 
+.unread-setter
+  :float right
+  :display none
+  :cursor pointer
+  :margin-top 8px
+
 .stream_container
   :min-height 500px
 
@@ -3139,7 +3145,8 @@ a.toggle_selector
   .notification_element
     :padding 10px
     :min-height 30px
-
+    &:hover
+      :background-color #FAFAFA
     > img
       :height 30px
       :width 30px