title: /undefined appearing lots of time in my 404 error log
body: <p>Basically in my error log i see lots of:</p>
  
  <pre><code>mysite.com/undefined (with referer coming from random pages of the website)
  
  User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
  </code></pre>
  
  <p>(and some other user agent)</p>
  
  <p>I have of course checked HTML or DOM for links with <code>/undefined</code> or something like that and there is just nothing. I have checked network tab with developer tools and on those page nothing requests <code>/undefined</code> (with my chrome).</p>
  
  <p>I have then setted a <a href="https://stackoverflow.com/a/11168326/496223">javascript logger</a> to save any error that come up. And in the log there isn't nothing that throws undefined or something like that... </p>
  
  <p>This is driving me crazy. Of course if i go on tihs page with my chrome, javascript doesn't print any error</p>
  
  <p>Notice: i have read everything <a href="https://stackoverflow.com/questions/11017609/undefined-randomly-appended-in-1-of-requested-urls-on-my-website-since-12-jun">here</a></p>
  
  <h2>Edit</h2>
  
  <p>Notice2: Beside that javascript error logger I have added an eventlistener (as explained in the answer linked)</p>
  
  <pre><code>$("body").on("click", "a[href$='undefined']", function() {
      window.onerror('Bad link: ' + $(this).html()); //alert home base
  });
  </code></pre>
  
  <p>And this never get triggered. (I have tested it with a manual /undefined link and the logger works)</p>
  
  <p>Also I found <a href="http://productforums.google.com/forum/#!topic/chrome/G1snYHaHSOc" rel="nofollow noreferrer">this topic</a> on google groups. Webmaster there are experiencing the same problem but no one has managed to nail down to the cause.</p>
  
  <p>Maybe it's some <strong>extension</strong> on chrome or any other browser that causes this requests.</p>