gistfile1.txt

versetile

A HTTP -> An HTTP?

in ABNF, you seem to be using # as a prefix indicating that a token is a list of such tokens, but I
don't believe that's ABNF or that you have it defined anywhere

"Follow the requirements from FTP to retrieve a resource." That's not nearly enough of course, at 
the very least a reference maybe?

"Prompt the end user for a username and password." I think that this is missing a step. If the user
cancels the prompt, return request (needs testing).

"Append a header named Access-Control-Request-Headers with value header value to preflight's
headers." -> does this mean that you have to include an empty ACRH header if there were no author
headers?

"If response's status is in the range 200 to 299" -> the *numeric* range, in case someone does
something stupid like "200" <= header <= "299" which in a number of languages will match for
"2000" or "21".