title: Adding additional attribute in <html> tag from nested page
body: <p>I have a tag <code>&lt;html&gt;</code> in <code>master page</code></p>
  
  <pre><code>&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
  </code></pre>
  
  <p>from another page that uses this master page I want to add one more attribute, finally I want to generate something like this:</p>
  
  <pre><code>&lt;html xmlns="http://www.w3.org/1999/xhtml" 
            prefix="ya: http://webmaster.yandex.ru/vocabularies/"&gt;
  </code></pre>
  
  <p>Does anyone know how this can be accomplished ?</p>