I tried adding the fix but now I get a

10:28:31,192 WARNING [com.icesoft.faces.webapp.CompatResourceServlet] failed to parse date: ti, 09 marras 2010 09:51:29 EET: java.text.ParseException: Unparseable date: "ti, 09 marras 2010 09:51:29 EET"
at java.text.DateFormat.parse(DateFormat.java:337) [:1.6.0_20]
at com.icesoft.faces.webapp.CompatResourceServlet.service(CompatResourceServlet.java:61) [:]

Strangely enough, before the fix the stuff it was trying to parse was in English.

This is annoying since I sometimes have resources denied (broken icons etc for compat-components) which I suspect is tracked to this issue (even if the parsing exception appears to be caught and log-warn-handled)

if I change my locale (with the applied fix) to en_US, I get a NFE for the blank string ""

Changed date formatter to always use English locale for parsing or formatting the HTTP dates.

To Nicklas Karlsson:

I believe that the <<java.text.ParseException: Unparseable date: "ti, 09 marras 2010 09:51:29 EET">> exception is caused by a request for a resource that was loaded before the fix for the date formatter was applied. The second time the browser requests the resource it just echoes the date it received the first time the resource was loaded, but after the fix the date formatter cannot parse it anymore since a different system wide locale was used.

SimpleDateFormat is not thread safe so it should not be declared static and reused in a class unless access to the code is synchronized.