Question css3 validation

Hi,
I've encountered a problem on your validator, few days before it was
saying that my web page is valid and there aren't any problems  in the
CSS3 standard and now im getting this error for each UL : error :
list-style-type (nullgenerate.html#propdef-list-style-type) none isn't
value list-style-type : none can you tell me what is the problem here ? as
i need to keep my web pages
valid because i have there the logo that the page was valid at time of the
test.....

Thanks.