Network Working Group R. Fielding Request for Comments: 2616 ...

there might exist some implementations that fail to accept anythingFielding, et al. Standards Track [Page 31]RFC 2616 HTTP/1.1 June 1999beyond the common forms.message-header = field-name ":" [ field-value ]field-name = tokenfield-value = *( field-content | LWS )field-content = The field-content does not include any leading or trailing LWS:linear white space occurring before the first non-whitespacecharacter of the field-value or after the last non-whitespacecharacter of the field-value. Such leading or trailing LWS MAY beremoved without changing the semantics of the field value. Any LWSthat occurs between field-content MAY be replaced with a single SPbefore interpreting the field value or forwarding the messagedownstream.The order in which header fields with differing field names arereceived is not significant. However, it is "good practice" to sendgeneral-header fields first, followed by request-header or responseheaderfields, and ending with the entity-header fields.Multiple message-header fields with the same field-name MAY bepresent in a message if and only if the entire field-value for thatheader field is defined as a comma-separated list [i.e., #(values)].It MUST be possible to combine the multiple header fields into one"field-name: field-value" pair, without changing the semantics of themessage, by appending each subsequent field-value to the first, eachseparated by a comma. The order in which header fields with the samefield-name are received is therefore significant to theinterpretation of the combined field value, and thus a proxy MUST NOTchange the order of these field values when a message is forwarded.4.3 Message BodyThe message-body (if any) of an HTTP message is used to carry theentity-body associated with the request or response. The message-bodydiffers from the entity-body only when a transfer-coding has beenapplied, as indicated by the Transfer-Encoding header field (section14.41).