[VE][249] Error Message Feedback

Could the error be explained in english it makes absolutely no sense to
me whatsoever. The DTD has been taken from your website and inserted
into the page, why would this cause an error I have no idea.

Validating http://www.cos-one.com/vbn.htm 
Error [249]: "DTDs other than base allowed only if CONCUR YES or
EXPLICIT YES" 

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