title: Facebook add thumbnail when sharing your site
body: <p>How can I add a thumbnail when using the facebook.com/sharer.php?u=mysite.com?
  I've added this to the header: <code>&lt;link rel="image_src" href="http://mysite.com/image.jpg"/&gt;</code></p>
  
  <p>But:
  1. It's not working (yet).
  2. It's not valid XHTML.</p>
  
  <p>Is there anyother way or am I doing something wrong?</p>
  
  <p>Thank you.</p>