Custom elements are not &quot;broken&quot; HTML. They&#x27;re very close to being a finalized standard, too:<p><a href="http:&#x2F;&#x2F;w3c.github.io&#x2F;webcomponents&#x2F;spec&#x2F;custom&#x2F;" rel="nofollow">http:&#x2F;&#x2F;w3c.github.io&#x2F;webcomponents&#x2F;spec&#x2F;custom&#x2F;</a>