title: What is this query string parameter: _sm_au_
body: <p>My app engine site redirects links to the site index page to the same URL with this query string appended: ?_sm_au_=iFVtD2FW4H4wSHS6.</p>
  
  <p>It only seems to happen in Chrome. Other browsers do not get redirected.</p>
  
  <p>I'm using the default App Engine Java framework. I'm not sure if the query string is coming from App Engine or from Chrome. I have been unable to find any documentation on <code>_sm_au_</code>.</p>