"keep the strictness" from what, though? Presto-Opera reported parse errors in the dev tools, for example (parse errors have a clear, unambiguous definition eve

"keep the strictness" from what, though? Presto-Opera reported parse errors in the dev tools, for example (parse errors have a clear, unambiguous definition even in the current HTML spec). DTD validation? As far as I'm aware, it would only be keeping it at a spec level—no implementation aside from validators ever implemented it. There's nothing stopping a browser from noting any validation error, though (and note they wouldn't just happen at parse time—they could happen following any DOM modification).