The Content-Length header is not returned in certain instances.
I believe this is an Apache behaviour when gzip compression is enabled (http://serverfault.com/questions/183843/content-length-not-sent-when-gzip-compression-enabled-in-apache).
I could also be a Cloudflare behaviour.
Regardless, this causes the self test to fail.
Thanks for your contribution. It sounds like this might be only happening in isolated cases, as I haven't seen this come up very often. So I'll keep this PR unmerged for a while and will try to get others with the same problem to test this out (I don't use Cloudflare).
In any case if you are using Cloudflare and you are also already using gzipped content, you are probably better served by our Speedster Advanced Extension.
Kewl. Figured I would pass it on.
Thanks for the products.
Thanks a lot, this was the solution to the selftest failing on nginx though it was working correctly. It appears the Content-Length header did not work. There are however a few double semicolons in app/code/community/Fooman/Speedster/Model/Selftester.php that shouldn't be there.