"display" property

When trying to validate my stylesheets I get errors because of the  
use of the "inline-block" value with "display" property.

The document http://www.w3.org/TR/2003/WD-CSS21-20030915/visuren.html  
says this value exists and is valid (obviously only for CSS 2.1 and  
CSS 3).

When validating using paste and copy to a text field (on http:// 
jigsaw.w3.org/css-validator/) CSS validates, when CSS 2.1 or 3 is  
selected, but with upload, referer-link or uri the same stylesheet  
doesn't validate - probably because the "inline-block" value was  
first introduced with CSS 2.1 and validator checks against CSS 2 and  
earlier?

Is this a bug?

Regards,

J. Buerger