It works fine with Chrome and it fails on an Android 2.3 browser – the page is performing an XmlHttpRequest to the server for a resource that just changed for sure and yet it gets back an older version. That’s the result of
a. the browser assuming a resource is cachable even if no Etag or Expires headers suggest so
b. the application not declaring the resource as non-cacheable.
Pagespeed rightfully reminds every time about resources without expiration header and this time it bit me – so this is a real thing.
George's Techblog 