the HTTP specification states that the Transfer-Encoding header is allowed for requests – but what error code should a server respond if it doesn’t understand that given Transfer-Encoding.
As far as I know the HTTP standard doesn’t cover this possibility, but maybe I have just overlooked it.
An unknown transfer-encoding should raise a HTTP error 501 ‘NOT IMPLEMENTED’. That’s what Apache does, at least.
Also see http://argray.com/unixfaq/httpd_error_codes.shtml
Edit: pointer to the corresponding RFC section: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.2