As long as the URI itself does not break the url()
syntax in any way (e.g. (
and )
must either be escaped or URI-encoded so they don't prematurely end the function token, also mentioned in the spec), it should be valid even if unquoted.
It's probably a validator bug. Specifically, it doesn't appear to handle unquoted data URIs in any form, because when I simply change data
to http
(even though it obviously doesn't resemble a typical HTTP address):
#something {
background: url(http:image/png;base64,ABCDEF);
}
... it then magically passes validation.