BUG? text-shadow doesn't exist

On checking 'www.rmwpublishing.net' I get the sole error:

100 h2 Invalid number : text-shadow Property text-shadow doesn't exist
: 2px 2px 2px #dedede

Which is strange as the words "text-shadow" link to
http://www.w3.org/TR/REC-CSS2/text.html#propdef-text-shadow which
don't say anything about it not been valid CSS.

I also think this maybe an error with the new Fuji' validator as it
comes up 'Invalid number' for what looks to be an internal error
number.

I know that there is very limited browser support for this property
but is it invalid?