URL

ISS Identity for the Web
Example: http://nick.iss.im
Where the iss channel is published: 
<link rel="service.feed" type="application/atom+xml"
title="iss" href="http://nick.iss.im/iss"/>

The avatar and nickname may be discovered consulting the hCard: 

<div class="vcard">
  <span class="fn n">
     <a class="url" href="http://nick.iss.im">
       <span class="given-name">Nick</span> 
       <span class="family-name">Vidal</span> 
     </a>
  </span>
  <span class="nickname">nickvidal</span>
  <img class="photo"
       src="http://nick.iss.im/wp-content/nick.jpg" />
</div>