问题
Is this valid HTML?
<!DOCTYPE html>
<html>
<head/>
<body>
<p>Hello, World</p>
<html>
<head/>
<body>
<p>Hello, World 2: Revenge of the Pointer</p>
</body>
</html>
<html>
<head/>
<body>
<p>Hello, World 3: GOTO null</p>
</body>
</html>
</body>
</html>
According to the HTML5 specs, the <html> element can be used:
- As the root element of a document.
- Wherever a subdocument fragment is allowed in a compound document.
It's the second part that I'm confused about. Does this mean that <html> is a "document" and any nested <html> is a "subdocument fragment"? How can I tell if this is "allowed"?
回答1:
No, that is not valid.
A compound document has a subdocument fragment declared inside it, which is a complete document in itself. You can't just use another html tag to make a compound document.
回答2:
As said by Guffa
A compound document is a document in itself and you can't use html to make a sub-document.
But a html may contain a iframe which is a sub-document and has html tag.
来源：https://stackoverflow.com/questions/32399301/is-it-valid-to-nest-html-inside-html