Assuming the top element of the document is allows validation of the document(s) against a given DTD.
As an alternative you can also try our non-DTD-based validator.
This is part of the XML 1.0 specification, and allows one to describe and verify that a given document instance conforms to the set of rules detailing its structure and content.
Backmapping is a powerful debugging/troubleshooting tool, one that you'll quickly grow to appreciate.
Configuration of a third-party DTD validation and parsing engine is done in the Options dialog box, as shown here.
By accessing the parse Error object, the exact error code, the error text, and even the line that caused the error can be retrieved: var xml Doc = new Active XObject("Microsoft.