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Is there anything wrong with writing parts of a webpage in XHTML with an HTML doctype?

Answer 1

+3 A:

It is 'okay' in the sense that almost every browser will render it correctly, but only because they're built to handle malformed HTML/XHTML/XML/whatever. However, any element(s) not matching the declared doctype (in your case, the HTML DTD) will prevent your code from validating, and it is, technically, malformed.

On the other hand, the vast majority of websites (even ones that render correctly) do not validate, so it's not a huge issue. I would stick to (strict) XHTML; note jimr's comment concerning self-closing tags (e.g. <img src="foo" />).

Nathan Clark 2009-06-24 21:09:56

Answer 2

+5 A:

HTML 5 allows for the use of XHTML syntax.

You can start using an HTML 5 doctype now which will push all browsers into standards mode, but be aware that new features of HTML 5 are only supported in some browsers.

From the Web Hypertext Application Technology Working Group:

Should I close empty elements with /> or >?

Void elements in HTML (e.g. the br, img and input elements) do not require a trailing slash. e.g. Instead of writing  , you only need to write  . This is the same as in HTML 4.01. However, due to the widespread attempts to use XHTML 1.0, there are a significant number of pages using the trailing slash. Because of this, the trailing slash syntax has been permitted on void elements in HTML in order to ease migration from XHTML 1.0 to HTML5.

The marvellously simple HTML 5 doctype looks like this:

<!DOCTYPE html>

So yes, you can write standards compliant HTML with self closing tags and it will validate against an HTML 5 validator. The industry has widely chosen to adopt HTML5 over XHTML2, and consequently I wouldn't recommend using XHTML for any new projects.

Edit: Just as a point of clarification, it is safe to use the HTML 5 doctype now, and it is also safe to assume that HTML 5 will be widely adopted over XHTML 2 given industry support. You can certainly author HTML 5 documents now, however many of the features of HTML5, such as <canvas> (notably lacking support from MS given that it competes with Silverlight) do not have cross browser support and are subject to change.

Bayard Randel 2009-06-24 21:10:12

What a great response, thank you so much!

noshoes 2009-06-24 21:28:30

But HTML5 is still a draft and subject to change. Don't rush into using it.

David Dorward 2009-06-24 21:33:30

The doctype is not going to change, but it would be prudent to take care using new features in HTML5.

Bayard Randel 2009-06-24 21:36:23

I agree with David.. Although I like some things that HTML5 offers.. I wouldn't commit yet.

natas 2009-06-24 21:36:37

Given that Google, Microsoft and pretty much every major industry body has pledged support for HTML 5, I think it's pretty safe to assume that's where the web is going. http://www.webmonkey.com/blog/Google_Throws_Its_Weight_Behind_HTML_5

Bayard Randel 2009-06-24 21:38:47

They haven't pledged to support it in it's exact current form. I said it was a draft and subject to change, not that the finished product would be unsupported.

David Dorward 2009-06-24 21:39:59

Answer 3

A:

<DOCTYPE> is a leave-over from SGML and should only appear once, at the top of the document. Adding other DOCTYPE declarations within the document would be a violation of both HTML and XHTML--though most browsers would probably forgive you.

If you must use both in a page, perhaps placing the nested document into an IFRAME would be more consistent with standards since IFRAMEs by definition house a separate window/document context.

Joe Davis 2009-06-24 21:12:03

I see what you're saying, but I only have one DTD at the top of my page. It's just that with a given DTD (HTML 4) I'm inclined to format things in an XHTML manner (like closing a p tag).

noshoes 2009-06-24 21:17:56

Answer 4

A:

No, it's not okay. In theory, at least. If you write XHTML syntax in a HTML document, it's invalid. Browsers will most likely render it the same way, but it's still invalid. Plus, the only thing valid in XHTML and invalid in HTML is a self-closing tag ( ). Just beacuse in HTML you're not required to close tags, doesn't mean you can't close them. You can write markup like this:

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent at enim sit amet urna placerat porttitor ut quis justo. Quisque posuere nisl ac libero dictum posuere. Suspendisse in magna neque. Donec et vestibulum sapien. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed at nulla dui.

<img src="" alt="">

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent at enim sit amet urna placerat porttitor ut quis justo.

See? It's valid HTML, and looks good.

BTW: read this.

Javier Badia 2009-06-24 21:23:35

XHTML syntax is valid in HTML 5 documents.

Bayard Randel 2009-06-24 21:24:45

HTML5 isn't finished. The choice of using it in a production environment is one that needs to be very carefully considered, and "liking the syntax better" is a very poor reason for choosing to use it.

David Dorward 2009-06-24 21:34:40

Answer 5

+4 A:

David Dorward 2009-06-24 21:32:52

Very informative, and you managed to answer all of my questions including a few I didn't ask. Thanks!

noshoes 2009-06-24 21:41:53

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Is there anything wrong with writing parts of a webpage in XHTML with an HTML doctype?

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