[XHTML 1.0 Strict] attribute shape on a defaulted from external subset

Hi,



I'm trying to validate an XHTML 1.0 Strict page and I get a lot of errors

like these:



 Line 26, Column 63: standalone: attribute shape on a defaulted from

external subset

 Line 36, Column 113: standalone: attribute method on form defaulted from

external subset



The validated URL is http://www.tty1.net/ .



I have no idea what the error description is trying to tell me, let alone

how to fix it. When I google for "defaulted from external subset", I find

some W3C document for CSS, but the validator does not seem to fetch the CSS

file from the server.



Any help is greatly appreciated.



Cheers,

Thomas