[cesarb]

From what I recall of that era, it's the exact opposite: invalid elements (like <noscript>) are simply ignored, and their contents shown. That's how <noscript> works: newer browsers which understand JavaScript know the <noscript> element and ignore its contents; older browsers which do not understand JavaScript don't know the <noscript> element so its contents are shown. The same trick is used for <noframes>: browsers like Netscape which understand frames don't show the contents of that element, while other browsers which don't understand <frame> and <frameset> will show the content of the <noframes> element, so it can be used as a fallback.

Strict validation of HTML came later with XHTML, but AFAIK all browsers which understand XHTML also understand JavaScript.

[shakna]

XHTML came after HTML 4.0, so it had its advent around the rise of JavaScript's popularity.

However, HTML 2.0, which you can find specified here [0], and it specifies the "ignore" behaviour. Short of spinning up an old VM, I think I'll trust that my memory hasn't failed me.

From RFC 1866:

> markup in the form of a start-tag or end-tag, whose generic identifier is not declared is mapped to nothing during tokenization. Undeclared attributes are treated similarly...

> For example: > <div class=chapter><h1>foo</h1><p>...</div> > => <H1>,"foo",</H1>,<P>,"..."

[0] https://www.w3.org/MarkUp/html-spec/

[bawolff]

If that was true, why did <script> tags have that horrible hack where the contents started with <!-- to hide from old browsers?

[shakna]

Note that in the example code I gave the enclosing tag vanished, but the internal tags did not. That's why.