W3C: at-rule namespace not implemented

[Leonatus]

At the end of editing a book with Sigil, I like to validate epubs with W3C also. There often appears the error: "Sorry, the at-rule @namespace is not
implemented."

On the top of my css appears: @namespace h "http://www.w3.org/1999/xhtml.

The books are readable, but I would like a correctly formed epub. Only that I have no idea what I'm doing wrong. Someone can tell me what I have to do, please?

[Toxaris]

Remove the @namespace. It should not be necessary.

[Leonatus]

Whee! That worked: "No error found". Thanks!

[Gregg Bell]

Originally Posted by Toxaris

Remove the @namespace. It should not be necessary.

Hey Toxaris. I ran into the same issue. (screenshot 193). Being a non-techie, so that just means I should remove just

@namespace

from the stylesheet? (screenshot 194)

And maybe, what purpose did it serve?

Thanks.

Actually I just tested it and it wanted me to remove:

@namespace "http://www.w3.org/1999/xhtml";

And then it showed the epub passed.

[Doitsu]

@Gregg Bell:

AFAIK, CSS namespace declarations are a CSS3-only feature and will always generate W3C error messages if the selected Stylesheet Validation Level is CSS Level 2.1.

You could theoretically change the CSS level via Edit > Preferences > Settings > General Settings, and if you change the value to CSS Level 3, the W3C validator will no longer display a namespace error message. However, selecting CSS Level 3 isn't recommended for epub2 book stylesheets, because the epub2 standard was based on CSS Level 2.1 and some older epub engines might not support CSS3-only elements.

Therefore it's better to simply delete CSS namespace declarations in epub2 books, unless the (X)HTML files contain non-standard namespace declarations.

AFAIK, CSS namespace declarations are only required for epub3 book stylesheets and only if you want to select elements with epub:type attributes.

For example the following stylesheet code:

@namespace epub "http://www.idpf.org/2007/ops";

*[epub|type='pagebreak'] { display: none; }

will hide epub3 page number targets formatted as:

<span epub:type="pagebreak" id="page1">1</span>

[Leonatus]

@Doitsu
Thank you for this explanation! I have always been wondering what the namespace declaration should be good for.

[Gregg Bell]

Originally Posted by Doitsu

@Gregg Bell:

AFAIK, CSS namespace declarations are a CSS3-only feature and will always generate W3C error messages if the selected Stylesheet Validation Level is CSS Level 2.1.

You could theoretically change the CSS level via Edit > Preferences > Settings > General Settings, and if you change the value to CSS Level 3, the W3C validator will no longer display a namespace error message. However, selecting CSS Level 3 isn't recommended for epub2 book stylesheets, because the epub2 standard was based on CSS Level 2.1 and some older epub engines might not support CSS3-only elements.

Therefore it's better to simply delete CSS namespace declarations in epub2 books, unless the (X)HTML files contain non-standard namespace declarations.

AFAIK, CSS namespace declarations are only required for epub3 book stylesheets and only if you want select elements with epub:type attributes.

For example the following stylesheet code:

@namespace epub "http://www.idpf.org/2007/ops";

*[epub|type='pagebreak'] { display: none; }

will hide epub3 page number targets formatted as:

<span epub:type="pagebreak" id="page1">1</span>

Thanks Doitsu. Yeah, I don't want to mess with the preferences so I'll just delete the namespace. But I do need to delete the below:

@namespace "http://www.w3.org/1999/xhtml";

correct?

Not just:

@namespace

correct?

[Doitsu]

Originally Posted by Gregg Bell

Thanks Doitsu. Yeah, I don't want to mess with the preferences so I'll just delete the namespace. But I do need to delete the below:

@namespace "http://www.w3.org/1999/xhtml";

correct?

Yes, you'll need to delete the complete line.

[Gregg Bell]

Originally Posted by Doitsu

Yes, you'll need to delete the complete line.

Thanks Doitsu. Appreciate it.