The error page I get because of issue 96 is malformed. It contains a head element inside the body element and a title element directly in the html element.

Then again, there is no document type declaration and no XML declaration, so maybe the server doesn't promise anything more than tag soup.

Having seen this I looked at a non-error page for comparison. What immediately caught my eye were stray html, head and body tags under "Active Releases Overview" and unescaped ampersands in some links, but Validator found 34 errors:
http://validator.w3.org/check?uri=https%3A%2F%2Fapps.fedoraproject.org%2Fpackages%2Fmysql-connector-python3

It's a wonder that browsers manage to make any sense at all of this mess.