The fact that it works is completely irrelevant. It has always worked, in about all versions of HTML/XHTML, in that type of simple cases.
The important fact is that omitting the html, body, head tags is valid markup.
Whether browsers conform to this is another matter. [1] suggests there are some issues with that.
The point of the post is that the syntax for writing html is getting better (just using 'html' as a doctype is great). But in terms of application, there is none.
If you want to write a web site/service and you want to support more users than just your friends, you have to do things right to support older browsers (and IE) and this means things like including all of the tags that FF/Chrome are automatically adding.
Before you ask what the minimal code for an HTML5 page is, you have to decide what constraints you are putting. Are you talking about the minimal valid, independent web page? The minimal code that your browser will parse as HTML and generate a DOM for? The minimal code that is allowed in an <iframe srcdoc>?
If you're talking about the minimal valid code for an independent web page, it is:
<!DOCTYPE html><title></title>
The title element is required, and is not automatically inserted if the tags are missing the way <html>, <head>, and <body> are.
If you're talking about the minimal thing the browser will parse, you can provide an empty document (with Content-type: text/html), and the browser will treat it as if it's an HTML document, generating the appropriate elements automatically. It will parse it in quirks mode, but if you don't care about validity, and are talking about an empty document, that doesn't matter much.
If you're talking about what you can embed in <iframe srcdoc>, again, an empty document is acceptable. In that context, the doctype and title are both optional.
The author mentions that you can leave the type attribute off of <script> tags. You can do the same with <style> tags as well, since it defaults to CSS.
It's worth adding that the DOCTYPE is what specifies what HTML rendering engine IE 7 and 8 use. A document without the DOCTYPE directive will render in quirks mode, and nobody wants that.
I think I recall Paul Irish once saying even closing tags of certain types (<li>, <p> etc) were also unnecessary. The start of the next tag should also signal the close of the previous one (unless you want to nest stuff) -- so whether the </p> or </li> tag or whatever is there or not makes no difference.
HTML parsers cope quite well with that (and have done for a while) but I don't do it. Although I am guilty of not bothering with the type declaration in scripts that are JavaScript <script src="..." />
The important fact is that omitting the html, body, head tags is valid markup. Whether browsers conform to this is another matter. [1] suggests there are some issues with that.
[1] http://stackoverflow.com/questions/5641997/is-it-necessary-t...