That's a very useful link, thank you. Here is a link to the result:

http://www.whatsmyip.org/http_compre...UxLjIyNi42MS8=

As you can see, the server is requesting compressed data as it's supposed to.

My problem then is why turning on GZIP compression from admin gives me the "invalid or unsupported form of compression" error.

The same site is uploaded, file for file, an exact copy at www.limelites.co.uk and it is GZIP enabled and working perfectly well.

So, is this a server issue, or a mod file or configuration issue?