Re: a href=" " gives a strange error message

Hi Mikhail,

The W3C Markup Validator is getting that message from the backend that it relies on for checking HTML5 docs.

And the backend is in turn getting that message from
the Jena IRI Library that is relies on for checking IRIs/URIs.

Here, from the Jena docs, is the explanation of DOUBLE_WHITESPACE:

  "Either two or more consecutive whitespace characters, or leading
  or trailing whitespace."

So despite the fact that the short name for the violation is 
DOUBLE_WHITESPACE, it can in fact be caused be a single whitespace
character. In this case, I guess the single space in your test
file could be considered either a leading or trailing space,
though there's actually no other content in the value for it to be
leading or trailing...).

The opacity of the error shortnames from the Jena IRI checker is
a known issue. I suppose one way that we might help mitigate it
is to take the DOUBLE_WHITESPACE text in the error message, and
turn it into a link that points to the explanation at the URL
above (and of course have the other messages from the library link
to the corresponding fragment IDs at that page).

I have filed a bug to that effect:


Mikhail Dvorkin <>, 2010-05-27 13:48 +0400:

> When validating an HTML5 document with the following tag:
> <a href=" ">...</a>
> (single space in href), the received error message looks strange:
> "Bad value for attribute href on element a: DOUBLE_WHITESPACE in PATH."
> Well, there is no double whitespace. Perhaps, this error message
> should be revisited.
> Thank you.
> Here's a source code that allows you to reproduce the error message:
> <html>
> <head><title>Title</title></head>
> <body>
> <a href=" ">single space in href</a>
> </body>
> </html>

Michael(tm) Smith

Received on Thursday, 27 May 2010 23:36:44 UTC