I see the point:
http://validator.w3.org/check?uri=http://www.nacse.org/~tichenom/testing/index.html
 give the following result:

This Page Is Valid XHTML 1.1!

Warning:
Line 196, column 16: character "<" is the first character of a delimiter but occurred as data

which is  XHTML 1.1. NOT XHTML 1.0 !!
As for XHTML 1.0 header should be 
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
but in  page http://www.nacse.org/~tichenom/testing/index.html , it contains XHTML1.1 header
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
So for XHTML1.1 validator,  pages are valid with only one warning. But for XHTML 1.0, the page is invalid. So maybe the CSS validator uses XHTML1.0 validator,  and then page fails validtaion.

ideas whizz
jozz

David Dorward wrote:
On Thu, Nov 18, 2004 at 01:15:08PM -0800, Michael Tichenor wrote:
  
I attempted to validate a page of mine ( 
http://www.nacse.org/~tichenom/testing/index.html ) and the validator gave 
an error saying to "validate your XML document first". It's valid XHTML
    

Actually, I don't think it is valid XHTML. See the XHTML 1.0
specification under "Differences with HTML 4: Script and Style
elements" (IIRC).

I suspect this comes under the heading of a limitation with XML of the
markup validator.