http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html 14.15 Content-MD5 The Content-MD5 entity-hea

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html 14.15 Content-MD5 The Content-MD5 entity-header field, as defined in RFC 1864 [23], is an MD5 digest of the entity-body for the purpose of providing an end-to-end message integrity check (MIC) of the entity-body. (Note: a MIC is good for detecting accidental modification of the entity-body in transit, but is not proof against malicious attacks.) Content-MD5 = "Content-MD5" ":" md5-digest md5-digest = <base64 of 128 bit MD5 digest as per RFC 1864> EDIT: I don't know if any browsers actually support this. I just configured an incorrect Content-MD5 header for a page and visited it in Chrome, Safari and Firefox and none of them complained about it.