app/views/notifications/_info_dropdown.html.erb
<% if @notifications.present? %>
<a id="num-of-notification" href="#" class="dropdown-toggle" data-toggle="dropdown">
<%= content_tag :span, class: ["num-of-notification", "label", "label-info"] do %>
<%= @notifications.length %>
<% end %>
</a>
<ul class="dropdown-menu notification" role="menu">
<% notifications.each do |notification| %>
<li role="presentation">
<%= link_to article_path(notification.article) do %>
<%= gravatar(notification.user, 40, class: ["media-object"]) %>
<span><%= notification_message(notification) %></span>
<% end %>
</li>
<% end %>
</ul>
<% else %>
<span class="navbar-text">
<%= content_tag :span, class: ["label", "label-default", "num-of-notification"] do %>
<%= @notifications.length %>
<% end %>
</span>
<% end %>