This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
The CSS validator at http://jigsaw.w3.org/css-validator/ outputs an "unknown" error if the percent sign is omitted in a linear-gradient color stop: body { background: linear-gradient(100deg, white 0, black 100%); } Whereas this validates fine: body { background: linear-gradient(100deg, white 0%, black 100%); } The way I read the spec it's OK to omit the unit: http://dev.w3.org/csswg/css3-images/#linear-gradients
Thanks for the report, it was indeed a bug in the code. Now fixed.