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RE: Whitespace before responses

From: Eric Lawrence <ericlaw@exchange.microsoft.com>
Date: Thu, 7 Jul 2011 20:08:27 +0000
To: Mark Nottingham <mnot@mnot.net>, Bjoern Hoehrmann <derhoermi@gmx.net>
CC: httpbis Group <ietf-http-wg@w3.org>
Message-ID: <479CAD406474484E8FA0E39E694732C017C9C334@DF-M14-02.exchange.corp.microsoft.com>
If I recall correctly, some browsers apply different rules for leading whitespace/junk based on whether it's a top-level document or not. 

IE (including IE9) are very liberal about ignoring unexpected junk preceding a HTTP response. For instance, IE will render bolded "Hello World" text when receiving this:

	This is not HTTP

	Is ItHTTP/1.1 200 OK
	Cache-Control: max-age=0
	Content-Type: text/html
	Connection: close

	<b>Hello world.</b>

In developing Fiddler, I ran across a few sites delivering HTTP/0.9 responses (e.g. without headers).  Here's an example: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=0&p=1&f=S&l=50&Query=IN%2FEric+Lawrence%0D%0A&d=PTXT which sends no headers, though it does lead the response with \n\n. It seems to render as a HTML document just fine in current versions of all major browsers.


-----Original Message-----
From: ietf-http-wg-request@w3.org [mailto:ietf-http-wg-request@w3.org] On Behalf Of Mark Nottingham
Sent: Tuesday, July 05, 2011 4:57 PM
To: Bjoern Hoehrmann
Cc: httpbis Group
Subject: Re: Whitespace before responses

On 04/07/2011, at 6:56 AM, Bjoern Hoehrmann wrote:

> * Mark Nottingham wrote:
>> <http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-14#section-3.1> says:
>>  In the interest of robustness, servers SHOULD ignore at least one  
>> empty line received where a Request-Line is expected.  In other  
>> words, if the server is reading the protocol stream at the beginning  
>> of a message and receives a CRLF first, it SHOULD ignore the CRLF.
>> Should a similar approach be taken when clients parse responses?
>> See also:
>> https://bugzilla.mozilla.org/show_bug.cgi?id=668168
> Well, we absolutely need to come to an agreement where messages start 
> and where they end. I would rather ask which behavior we are more 
> like- ly to agree on. Apart from that it's obviously best if nothing 
> has to be skipped, as skipping requires more work than not skipping.

>From a quick test, Firefox and Chrome will skip at least two blank lines (without any whitespace on them); Opera will offer to download it as a file (!). Safari and Curl consider the whitespace and headers as the body (i.e., displaying it), as per HTTP/0.9. I don't have access to IE at the moment, but AIUI it'll operate as FF and Chrome.

Interestingly, Safari sniffs the response; if it looks like HTML, it will display it as such. I guess HTTP/0.9 by definition requires sniffing.


Mark Nottingham   http://www.mnot.net/
Received on Thursday, 7 July 2011 20:08:57 UTC

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