Why is http://data-vocabulary.org/Person in the css as a messageUserInfo class attribute?

[Paul B]

I was just checking some of the css, as you do....and I noticed the messageUserInfo class has an attribute linked to this site: http://data-vocabulary.org/Person

I don't think I've ever seen that before so I was wondering what purpose it served.

Can Mike or Kier explain? Just me being nosey is all.

 

[Shadab]

They are using Microdata format to semantically markup author (user) information:
ie, your name, title and photo.

<div class="messageUserInfo" itemscope itemtype="http://data-vocabulary.org/Person">
     <div class="messageUserBlock">
         <div class="avatarHolder">
             <a class="avatar Av521m" itemprop="photo" data-avatarHtml="true">
                 <!-- Avatar -->
             </a>
         </div>
         <h3 class="userText">
             <a class="username" itemprop="name">Brogan</a>
             <em class="userTitle" itemprop="title">Well-Known Member</em>
         </h3>
     </div>
 </div>

You can read more about it over here: People - Google Webmaster Central.
(check the html source given under the 'Microdata' heading near the end of the page)