yes. "Implied LWS" rule says it can be included between any tokens, but tokens MUST be separated by a delimiter therefore if 0.000 is allowed (no delimiters) th

yes. "Implied LWS" rule says it can be included between any tokens, but tokens MUST be separated by a delimiter therefore if 0.000 is allowed (no delimiters) then it means it is a single token and "implied LWS" rule is not applicable for the 0.000 part in the quality values: * implied LWS The grammar described by this specification is word-based. Except where noted otherwise, linear white space (LWS) can be included between any two adjacent words (token or quoted-string), and between adjacent words and separators, without changing the interpretation of a field. At least one delimiter (LWS and/or separators) MUST exist between any two tokens (for the definition of "token" below), since they would otherwise be interpreted as a single token.* </quote> http://www.ietf.org/rfc/rfc2616.txt http://www.ietf.org/rfc/rfc2616.txt Quality values: qvalue = ( "0" [ "." 0*3DIGIT ] ) | ( "1" [ "." 0*3("0") ] ) It seems the author is mistaken in allowing: 0 . 0 0 0