anchor.diff:  
           <div class="block region">
             <h3><%= @site.word_for_regions %></h3>
  -          <select name="regions_ids" multiple>
  -            <option default>All regions</option>
  +          <select name="regions_ids" multiple placeholder="All regions">
               <% @regions.each do |region| %>
                 <option value="<%= region.id %>"><%= region.title %>, <%= region.subtitle %></option>
               <% end %>
  
positive.code: 
          <div class="block donor">
            <h3>Donor</h3>
            <select name="donors_ids" multiple>
              <option default>All donors</option>
              <% @donors.each do |donor| %>
                <option value="<%= donor.id %>"><%= donor.title %></option>
              <% end %>
  
negative.code:         <% if @navigate_by_cluster %>
            <div class="block cluster">
              <h3><%= @site.word_for_clusters %></h3>
              <select name="clusters_ids" multiple placeholder="All clusters">
                <% @clusters.each do |cluster| %>
                  <option value="<%= cluster.id %>"><%= cluster.title %></option>
                <% end %>
  