title: Setting outbound 'Expires:' in Squid server's HTTP header
body: <p>I'm having a problem where items served by my Squid server are being cached by Limelight for too long, sometimes days.  It happens when a piece of content has been static for a long time (weeks) and then undergoes numerous changes in a matter of hours.</p>
  
  <p>Limelight gets its content from our Squid server and I'm told that if I can add 'Expires: 15m' in the HTTP header the Squid server sends, Limelight will not cache the image for more than 15 min.</p>
  
  <p>Unfortunately, I can fond no setting in Squid that will allow me to add this to the header.</p>
  
  <p>Here's the HTTP header as presently being sent:</p>
  
  <blockquote>
  <pre><code>HTTP/1.0 200 OK
  Date: Tue, 15 Dec 2009 23:57:33 GMT
  Server: nginx/0.5.26
  Content-Type: image/jpeg
  Content-Length: 83843   
  Last-Modified: Tue, 15 Dec 2009 23:52:00 GMT
  Accept-Ranges: bytes
  Age: 450
  X-Cache: HIT from squid01.prod.mydomain
  X-Cache-Lookup: HIT from squid01.prod.mydomain:3128
  Via: 1.0 squid01.prod.mydomain:3128 (squid/2.6.STABLE14)
  Connection: close
  </code></pre>
  </blockquote>