To expand a bit more: > Wikipedia gives this as an example of a standard that changed: https://github.com/whatwg/dom/issues/319 https://github.com/whatwg/dom/i

To expand a bit more: > Wikipedia gives this as an example of a standard that changed: https://github.com/whatwg/dom/issues/319 https://github.com/whatwg/dom/issues/319 That's the reason why tests 23 and 25 fail (both because of the "wrong" exception being thrown); https://github.com/web-platform-tests/wpt/commit/3cbdbaa7ca93e3c81b38f2d489eef1e6ea71b6c6 https://github.com/web-platform-tests/wpt/commit/3cbdbaa7ca9... is the Acid3 change for that. The other test that fails, test 35, is down to https://www.w3.org/Style/CSS/Tracker/issues/317; https://www.w3.org/Style/CSS/Tracker/issues/317; https://github.com/web-platform-tests/wpt/commit/e6f63a6e69ea785bbb554c4b9dd107ae2ea7e524 https://github.com/web-platform-tests/wpt/commit/e6f63a6e69e... is the Acid3 change for that. (The reason they're simply commented out is it follows the precedent set by Hixie when he was still maintaining Acid3, c.f., https://github.com/web-platform-tests/wpt/blob/master/acid/acid3/test.html#L597 https://github.com/web-platform-tests/wpt/blob/master/acid/a..., plus there are other feature-specific tests for those features in WPT.)