Yeah, but the SGML declaration for HTML contains SHORTTAG, so <a href=../bar/index.html>Bar</a> is actually shorthand for the invalid <a href="..">bar</a

Yeah, but the SGML declaration for HTML contains SHORTTAG, so <a href=../bar/index.html>Bar</a> is actually shorthand for the invalid <a href="..">bar</a>index.html>Bar</a> Good luck reading real world HTML with a browser that implements that correctly. (And that is why the W3C validator so often complains about a closing A tag that is not open (or at least used to do). )