When the conversion process loads an XML or SGML document, it uses an XML or SGML parser to convert text into a usable document. Some documents may contain parser errors, text patterns not allowed by the XML and SGML standards. By default, the conversion processor ignores parser errors and does its best to process each document as if it were correctly formed.

If you specify return-parser-errors=yes and the input SGML or XML document contains errors, the conversion processor will return an XHTML document listing the errors.