discourse/app/views/categories/index.html.erb

<div itemscope itemtype='http://schema.org/ItemList'>
  <meta itemprop='itemListOrder' content='http://schema.org/ItemListOrderDescending'>
  <table class='category-list'>
    <thead>
      <tr>
        <th class='category'><%= t 'js.categories.category' %></th>
        <th class='topics'><%= t 'js.topic.list' %></th>
      </tr>
    </thead>
    <tbody>
      <% @category_list.categories.each_with_index do |c, index| %>
        <tr>
          <td class='category' style='border-color: #<%= c.color %>;'>
            <div itemprop='itemListElement' itemscope itemtype='http://schema.org/ListItem'>
              <meta itemprop='position' content='<%= index %>'>
              <meta itemprop='url' content='<%= c.url %>'>
              <h3>
                <a href='<%= c.url %>'>
                  <span itemprop='name'><%= c.name %></span>
                </a>
              </h3>
              <div itemprop='description'><%= c.description&.html_safe %></div>
              <% if c.subcategory_list.present? %>
                <div class='subcategories'>
                  <% c.subcategory_list.each_with_index do |sc, index| %>
                    <a href='<%= sc.url %>'><%= sc.name %></a>&nbsp;
                  <% end %>
                </div>
              <% end %>
            </div>
          </td>
          <td class='topics'>
            <div title='<%= c.topic_count %> <%= t 'js.topic.list' %>'><%= c.topic_count %></div>
          </td>
        </tr>
      <% end %>
    </tbody>
  </table>
</div>

<% content_for :title do %><%= @title %><% end %>

<% content_for :head do %>
  <%= raw crawlable_meta_data(title: SiteSetting.title, description: SiteSetting.site_description) %>
<% end %>