Why isn't there a space before "Safe"? New compact http headers saving one character?
The field value MAY be preceded by any amount of LWS, though a single SP is preferred.
For the definition of SP and LWS, see: http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2.2
For the definition of MAY, see: https://www.ietf.org/rfc/rfc2119.txt