I'm getting this error when trying to validate my css.......

org.xml.sax.SAXException: Please, fix your system identifier (URI) in the DOCTYPE rule.

...and here's the DOCTYPE rule

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
" http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">


Any help appreciated guys.

Regards