growbt

 <span itemscope="" itemref="[Shape]" itemtype="http://growbutton.com/ns#button">
   <span itemprop="url">[URL]</span>
   <span itemprop="title">[Title]</span>
   <span itemprop="image">[Image]</span>
   <span itemprop="apikey">[ApiKey]</span>
 </span>

[Shape] : square or rectangle, Shape of the Grow! button
[URL]   : URL of the content page
[Title] : Title of the content page