I've read around that XHTML 4.01 does not has the data- attribute. Unfortunately my class calls for the use of XHTML. I need to embed a twitter widget and it works however the site won't validate.
a class="twitter-timeline" href="https://twitter.com/row2k" data-widget-id="654806159795183617">Tweets by #row2k</a>
Can anyone help assign the "data-widget-id" another way so that the widget will run as well as validate?
If you're not using any entity references such as (or if you can replace them all by numeric references like ), you can use the <!DOCTYPE html> header and then it will work AND validate.
By the way, there is no such thing as XHTML 4.01; You meant XHTML 1.0 surely, the equivalent of HTML 4.01.
I have a .NET Master page with an XHTML DTD: !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional ... >.
My .NET .ascx input controls need to start using the HTML5 placeholder attribute. It's my understanding that browsers won't recognize placeholder unless the HTML5 DTD is used: <!DOCTYPE html>.
I'm leery about simply changing the Master page to use the HTML5 doctype. I've heard that the HTML5 spec is supposed to backwards support XHTML markup, but I'm wondering about any other adverse side-effects with this kind of blanket change. Does anyone have insight regarding this?
Note: Several web apps use the Master page so it would be a widespread change.
HTML5 is designed to be backwards compatible with XHTML and HTML so developers can easily migrate.
The only effect for you will be that the browser will not enforce the strict XHTML rules.
You can still follow the XHTML rules however but you aren't forced to.
So you can safely edit your doctype to the HTML5 doctype!
Is it valid XHTML / good practice to have links of the following form?
//www.example.com/foo/bar.html
If the current page is HTTP, then the link points to: http://www.example.com/foo/bar.html
If the current page is secured under HTTPS, then the link points to: https://www.example.com/foo/bar.html
In other words, is
<a href="//www.example.com/">
valid in XHTML 1.1 Strict? And, is it supported by many/all browsers?
Is it valid XHTML
Completely. XHTML doesn't care about the syntax of URIs. The href attribute is defined as containing CDATA.
valid in XHTML 1.1 Strict?
There is no such language.
XHTML 1.0 has Strict / Transitional / Frameset versions.
XHTML 1.1 is just XHTML 1.1. (And isn't blessed by rfc2854 for serving as text/html (which you need for IE < 9 support)).
And, is it supported by many/all browsers?
Yes. Support is fine.
I'm having a rather heated debate into IE's XHTML Compatibility. The only thing is, I'm unsure if the guy is trolling.
Essentially he claims that IE has absolutely no XHTML compatibility, and that a document with a defined XHTML doctype means absolutely nothing when served as content type text/html, regardless of the browser used.
I do not believe this and sources say otherwise, but I am wrong?
Edit: Disregarding IE, does it still mean that when XHTML is defined in an HTML document it is NOT XHTML? Like the guy suggested? My current understanding is that XHTML is often contained within the HTML content type. This means that technically you could say that XHTML is merely HTML unless the correct content-type is used. But it's still XHTML syntax and so it a little confusing.
You can find the thread in question over at digitalpoint forums.
IE has indeed no support for application/xhtml+xml content type while other browsers would then handle HTML as XML. When text/html is used, every browser will just handle XHTML as HTML, IE does nothing different here (expect from the usual quirks).
More details here: http://hsivonen.iki.fi/doctype/
The guy is right. When serving XHTML as text/html, is is no longer XHTML, but funny-looking HTML. MIME type is key.
I guess this question is done, but:
IE has absolutely no XHTML compatibility
IE won’t parse XHTML content served as text/html as XHTML. (It’ll parse it as HTML.)
Unfortunately, it won’t display XHTML content served as application/xhtml+xml as a web page — it’ll display it just like it displays any other XML content, i.e. prettified source.
As per the XHTML 1.0 spec, you are allowed to serve it as text/html for compatibility with older browsers (i.e. IE). So IE is sort of compatible with the XHTML 1.0 spec. But as many have argued, if you’re not parsing XHTML as XML, what’s the point?
a document with a defined XHTML doctype means absolutely nothing when served as content type text/html, regardless of the browser used
Depends what he means by “means”. It’s still HTML, so it’s got all the meaning associated with that. And as you say, the content is still XHTML, as it’s written in the XHTML syntax. But it won’t be parsed as XML due to the mimetype, so in that sense it’s not XML, and thus isn’t XHTML.
(If you’re wondering what the practical implications of this are, join the club.)
BalusC is correct. More to the point is that the person you are arguing with is assuming that XHTML must be XML, which is false. XHTML 1.0 is a syntax of HTML that is compatible with XML syntax, but is however an SGML serialization that may optionally be processed as XML per paragraph 5.1 of the specification. XHTML 1.1, however, must be processed as XML.
The idea is that XHTML 1.0 is written as a transitional point between SGML and the XML syntax, even XHTML 1.0 strict. The various doctypes of XHTML 1.0 are all transitional and merely indicate the degree of conformance to the XML syntax without regard for the method of processing.
The other guy is right. You are wrong. IE has no support for application/xhtml+xml as others have said. IE treats it as "tag soup" when served as text/html as do other browsers.
It seems that HTML 5 is going to be supported (partially) by Firefox 3.1 and other browsers. It is adding support for video and audio as tags, but these are new tags that XHTML 1.0 Transitional does not recognize. What is the behavior supposed to be if I use a new HTML 5 tag in a future version of Firefox but use the DTD for XHTML? And what if I mix HTML 5 markup with XHTML 1.0 Trans?
This is getting confusing. Why didn't they just add these tags to XHTML? How do we support both XHTML and HTML 5?
Video on HTML 5: http://www.youtube.com/watch?v=xIxDJof7xxQ
HTML5 is so much easier to write than XHTML 1.0.
You don't have to manually declare the "http://www.w3.org/1999/xhtml" namespace.
You don't have to add type attributes to script and style elements (they default to text/javascript and text/css).
You don't have to use a long doctype where the browser just ignores most of it. You must use <!DOCTYPE html>, which is easy to remember.
You don't have a choice to include or not include a dtd uri in the doctype and you don't have a choice between transitional and strict. You just have a strict doctype that invokes full standards mode. That way, you don't have to worry about accidentally being in Almost standards mode or Quirks mode.
The charset declaration is much simpler. It's just <meta charset="utf-8">.
If you find it confusing to write void elements as <name>, you can use <name/>, if you want.
HTML5 has a really good validator at http://validator.nu/. The validator isn't bound by a crappy DTD that can't express all the rules.
You don't have to add //<![CDATA etc. in inline scripts or stylesheets (in certain situations) to validate.
You can use embed if needed.
Just syntax-wise, when you use HTML5, you end up with cleaner, easier to read markup that always invokes standards mode. When you use XHTML 1.0 (served as text/html), you're specifying a bunch of crud (in order to validate against a crappy dtd) that the browser will do automatically.
Myths and misconceptions abound in this thread.
XHTML 1.0 is older than HTML 5. It cannot use any new vocabulary. Indeed, its main selling point was that it uses exactly the same vocabulary as HTML 4.01.
There will be no XHTML 1.2 - most probably. And it is not needed. XHTML 5 is the XML serialization of HTML 5. Identical vocabulary, different parsing rules.
HTML has never been treated as true SGML in browsers. No browser has ever implemented an SGML-compliant parser. HTML 5 will make this fact into a rule and the HTML serialization will follow todays de facto standard. One could perhaps say that it is "SGML-ish".
As it has been stated, the DTD serves exactly one purpose IN BROWSERS, and that is to distinguish between standards compliance mode and quirks mode. Thus it affects only styling and scripting. If you are using frames on a page with astrict doctype, they will render just fine. As will <embed> and even <marquee> - even though the latter is an abomination and the former not in any current standard. It is part of HTML 5, though.
Video and audio can be used regardless of serialization, XML or HTML. they are part of both HTML 5 and XHTML 5. Once the parsing stage is over a browser will have constructed an internal DOM of the document. That DOM will be for all practical purposes the same regardless of serialization. And yes, XHTML sent with text/html is still normal html, regardless of doctype.
Well, generally speaking HTML is SGML and XHTML is expressed in XML. Because of that, creating XHTML is connected with more restrictions (in the form of markup) than HTML is. (SGML-based versus XML-based HTML)
As mentioned on Wikipedia, HTML 5 will also have a XHTML variant (XHTML 5).
Rule of thumb: You should always use valid markup. That also means that you should not use the mentioned <video> or <audio> tags in XHTML 1.0 Transitional, as those are not an element of that specification. If you really need to use those tags (which I highly doubt), then you should make sure that you use the HTML 5/XHTML 5 DTD in order to specify that your document is in that DOCTYPE.
Using HTML 5 or XHTML 5 in the given state of the implementation (AFAIK, the standard is not even settled, yet, correct?) could be counter-productive, as almost all users may not see the website rendered correclty anyways.
Edit 2013:
Because of the recent downvotes and since this accepted answer cannot be deleted (by me), I would like to add that the support and standardization process of HTML5 is nowadays totally different to what it was when I wrote this answer five years ago. Since most major browsers support most parts of the HTML5 draft and because a lot of stuff can be fixed with polyfills in older browsers, I mainly use HTML5 now.
You might be looking at the problem the wrong way because the relationship to XHTML 1.x section, HTML 5 states:
"This specification is intended to replace XHTML 1.0 as the normative definition of the XML serialization of the HTML vocabulary."
Now that language is controversial (the XHTML 2 WG has disputed it and the HTML WG is trying to resolve the differences...) but that's where we stand right now.
A couple of notes:
HTML 5 includes an XML serialization known as XHTML 5, the spec explains the differences if you're into nitty gritty details
HTML is not SGML. Henri Sivonen has done a great write up on the history of HTML parsing
As of this time (it has been a topic of debate several times), there won't be a DTD for HTML/XHTML 5 -- the Conformance Requirements section of the spec explains why a DTD isn't suitable for defining the HTML language. The HTML 5 validator also contains a wealth of information on this topic (including RELAX NG schemas for HTML5)
Keep in mind that doctypes only serve one purpose in browsers: switch between quirks, almost standards and standards mode. Therefore, using <video> and <audio> will work with any doctype declaration. IMO, using an XHTML doctype is quite useless, as every page you send with text/html MIME type is parsed as (tag-soup) HTML anyways. I suggest using the HTML5 doctype (<!doctype html>), as it is easier to remember and doesn't force you in XML syntax without a reason.
Why didn't they just add these tags to
XHTML?
They actually did, there is an XML serialization of HTML 5 (XHTML5). To use this, you have to send your pages with an XML MIME type, such as application/xhtml+xml. This is not (yet) supported by IE, though.
What is the behavior supposed to be if
I use a new HTML 5 tag in a future
version of Firefox but use the DTD for
XHTML?
And what if I mix HTML 5 markup with
XHTML 1.0 Trans?
If your markup isn't implemented as part of your chosen DTD - then logically, that markup shouldn't be followed. But browser implementations aren't always strictly logical.
Why didn't they just add these tags to
XHTML? How do we support both XHTML
and HTML 5?
xHTML is not better than HTML, but it's more suited to some applications. One of the main benefits of xHTML is that it can be transformed into different formats using XSLT. For example, you could use XSLT to automatically transform xHTML into an RSS feed or another XML format.
You don't need to support both formats - weigh up the benefits/drawbacks for each with your project's requirements. HTML 5 probably won't be standard for quite some time.
(X)HTML5 is just the next version. You should be using XHTML1.1 until XHTML5 is well-supported.
You probably should not use the backwards-compatability SGML profile of HTML5. It makes things harder for scrapers and small parsers.
Your doctype will tell the browser whether you're using HTML5 or XHTML. You can't just shove a tag from one doctype into a document of another doctype and expect it to work.
Without a doctype, it's all just tag soup anyway.
Don't use things like video/audio tags when 99% of people won't be able to view it properly on their browser. For either of these two examples I'd suggest using FLV.
As far as why they don't add it to XHTML... firstly 1.0 isn't the most recent version, 1.1 was released a while ago.
Eventually things get standardized and we'll see these types of tags in both standards, but for now just do what you can to ensure the most amount of people can view your content.