W3C home > Mailing lists > Public > www-validator-css@w3.org > October 2007

Re: Real problem caused by CSS validators willingness to tacitly accept HTML

From: Jukka K. Korpela <jkorpela@cs.tut.fi>
Date: Wed, 31 Oct 2007 15:43:45 +0200
Message-ID: <001501c81bc4$120a3d20$0300000a@DOCENDO>
To: <www-validator-css@w3.org>

Philip Taylor (Webmaster) wrote:

> 1) The CSS validator is asked to validate a non-existent CSS page
> http://jigsaw.w3.org/css-validator/validator?uri=http://www.rhul.ac.uk/resources/Stylesheets/CSS/TP-Common.css

Technically, it is asked to check a resource that does not exist. A 
nonexistent resource has no type, so we can't call it a non-existent CSS 

> 2) The CSS Validator says that validation was successful, and
> displays the CSS.

To me, it says

Target: http://www.rhul.ac.uk/resources/Stylesheets/CSS/TP-Common.css
I/O Error: http://www.rhul.ac.uk/resources/Stylesheets/CSS/TP-Common.css: 
Not Found
which is not optimal (I'd prefer seeing a clear indication of the "Not 
Found" response, with the HTTP error code) but not incorrect either.

> The IIS is configured to serve a custom 404 (HTML) web
> page on encountering a 404,

That's fine, though the server is also configured to include nonsense in its 

"The Web site you are trying to access has an IP address that is configured 
not to accept requests that specify a port number."

> and this page page links
> to a subtly different version of the CSS file intended
> to be specified at (1) above.

It seems that you have somehow encountered a situation where the W3C CSS 
Validator treats the error message page (accompanying the 404 response) as a 
response to the request. That would be a mistake, a protocol error, but I 
cannot construct the situation. _If_ it happens, the rest is natural, since 
the W3C CSS Validator is _supposed_ to handle HTML documents as well.

> This behaviour has
> now been changed to simplify urgent work here; it
> may be re-instated in due course,

Sorry, I don't follow.

> but attempts to
> replicate the problem will currently shew very different
> CSS between
> http://jigsaw.w3.org/css-validator/validator?uri=http://www.rhul.ac.uk/resources/Stylesheets/CSS/TP-Common.css
> and
> http://jigsaw.w3.org/css-validator/validator?uri=http://www.rhul.ac.uk/resources/Style-sheets/CSS/TP-Common.css

The former results in information about I/O error, the latter results in a 
report on checking CSS code. These behaviors seem to correct to me. They 
_must_ differ very much, since the former refers to a nonexistent resource 
and the latter to a stylesheet.

> Request : could the CSS validator /please/ report (very
> loudly !) if the returned resource is declared at
> HTTP level to be anything other than "text/css",

The W3C CSS Validator is capable of handling HTML documents as well, and 
this is a _very_ useful thing and should not be disturbed. If there is or 
was a problem, it was in the handling of HTTP error responses.

> and could it also please report if the served file
> appears not to be CSS but (say) HTML with CSS embedded
> or linked ?

I don't think there's a reason to make a noise about that, since it's 
intended behavior and clearly indicated in the user interface for submitting 
a URL for checking.

But admittedly the wording is slightly misleading when it says

"This document validates as CSS!"

for a document that is not a CSS stylesheet. An adequate statement would be 
something like

"The CSS style sheets included in the submitted document or referred to by 
it are syntactically correct."

Jukka K. Korpela ("Yucca")
This message validates as English! 
Received on Wednesday, 31 October 2007 13:42:30 UTC

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