The document located at: http://www.w3.org/MarkUp/html40-updates/html40-errata.html
does contain some errors itself:
Found by me are:

errors reported for sections 12.1.1 and 12.1.2 begin with the words 'Then sentence' which in both cases should be 'The sentence'
the general error reported for section 16 has a comma at the end of the hyperlink 'section 16,', no other headings have this comma

Great work!