The HTML 3.1 specification is essentially irrelevant for implementing a modern browser; and you certainly don't need HTML 5.0, and, HTML 5.1, and HTML 5.2, and

The HTML 3.1 specification is essentially irrelevant for implementing a modern browser; and you certainly don't need HTML 5.0, and, HTML 5.1, and HTML 5.2, and HTML 5.3, and, HTML 4.0, and, HTML 4.01, and, HTML 3.2, and, XHTML 1.0, and, XHTML 1.1, and, XHTML 2. These are large documents; possibly the largest in the set. It takes a minute to spot-check; some specific examples were provided in the previous thread. I don't have the list any more and can't be bothered to recreate it; what value is there if you can just check Drew's list – which is really not that hard? I also have no idea how correct it is, exactly; I suspect the actual number would be even lower still.