Drupal 7.27: 408 Request time out in Chrome browser
This is a Chrome bug. 

https://meta.stackexchange.com/questions/208790/408-request-time-outs-still-continues/232275#232275

One solution: http://blog.haproxy.com/2014/05/26/haproxy-and-http-errors-408-in-chrome/

Seems to be limited to Chrome, page requests through http:// and servers running HAProxy.