I don't call that fragile, I call that well-founded. It has always perturbed me that, when encountering an error, HTML parsers will guess what they think you meant instead of throwing it back. I don't want my parser to do guesswork with potentially undefined behavior. I don't want my mistakes to be obscured so they can later come back to bite me - I want to be called out on issues loud and clear before my users see them.

Perhaps it works under the context of manually-authored markup with minimal effort, so I can see why the choice was made. These days it's yet another reason why the web is a precarious pile of sticks. HTML freely lets you put a broken oddly-shaped stick right in the middle and topple the whole stack.

The people turning the web from a handcrafted document sharing system into the world's premiere application platform should have made XHTML win.

Oh, and JavaScript.

XML didn't "emerge" and was repurposed for HTML; it was designed for new vocabularies on the web. The first sentence of the XML spec reads:

> The Extensible Markup Language (XML) is a subset of SGML that is completely described in this document. Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML.