When I use to write pages in XHTML. I had 3 types of doctype - strict, transitional and frameset.
Do we have them in HTML5?
the html5 doctype is
<!DOCTYPE html>
When you use the new HTML5 DOCTYPE, it triggers browsers to render the page in standards compliant mode.
Standards-compliant mode
In standards-compliant mode, the web browser assumes the page has been authored to the web content specification declared; code that does not conform to the declared standard may not display, or may display incorrectly.
For a web browser’s standards-compliant mode to be triggered, the webpage must have a complete document type declaration, including the URI to the document type definition (DTD).
There is typically less variation in webpage display between different browsers when standards-compliant mode is triggered, as the same centralised W3C specification is used as a reference when creating the web browser software.
Courtesy this link
No, the HTML5 doctype
<!DOCTYPE html>
is unique, since it was chosen as the shortest doctype (string) able to turn all current browser (even IE6, afaik) in standard mode (and it can be written in upper/mixed case)
HTML 5 requires a doctype for legacy compatibility. It has a short doctype <!DOCTYPE html> and a long doctype <!DOCTYPE html SYSTEM "about:legacy-compat"> The long doctype is only for systems that cannot generate the short one. - HTML 5 specification
No, HTML5 is just HTML5, there are no subsets.
There is but one:
<!DOCTYPE html>
The standard required preamble in the HTML serialisation of HTML5 (i.e. when served as text/html) is
<!DOCTYPE html>
Some HTML generators, most notably XSLT, have difficulty creating the above doctype. They may use
<!DOCTYPE html SYSTEM "about:legacy-compat">
In the XML serialisation of HTML5 (i.e. when served as application/xhtml+xml), the doctype may be either of the above, or it may be omitted entirely.
Note that these variations are not like strict, transitional or frameset. What is valid and invalid in HTML5 is the same for each of the above variations - leaving aside the orthogonal matter of differences between HTML and XML syntax.
HTML5 has only one and that is:
<!DOCTYPE html>
Related
Why is <!DOCTYPE html ... > used in html file?
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
The DOCTYPE Declaration (DTD or Document Type Declaration) does a couple of things:
When performing HTML validation testing on a web page it tells the HTML (HyperText Markup Language) validator which version of (X)HTML standard the web page coding is supposed to comply with. When you validate your web page the HTML validator checks the coding against the applicable standard then reports which portions of the coding do not pass HTML validation (are not compliant).
It tells the browser how to render the page in standards compliant mode.
For more information refer to this "<!DOCTYPE html>" What does it mean?
It tells the browser that the following code is to be treated as a particular version of html code.
The browser knows then to look for an open HTML tag <html> and treats everything like html until it reaches the close HTML tag </html>
<!DOCTYPE html> is all that's needed now.
The term DOCTYPE tells the browser which type of HTML is used on a webpage. Here is link of official page which explains your query why and what is
<!DOCTYPE html>
A doctype defines which version of HTML/XHTML your document uses. You would want to use a doctype so that when you run your code through validators, the validators know which version of HTML/XHTML to check against
The declaration is not an HTML tag; it is an instruction to the web browser about what version of HTML the page is written in.
In HTML 4.01, the declaration refers to a DTD, because HTML 4.01 was based on SGML. The DTD specifies the rules for the markup language, so that the browsers render the content correctly.
HTML5 is not based on SGML, and therefore does not require a reference to a DTD.
Tip: Always add the declaration to your HTML documents, so that the browser knows what type of document to expect.
The <!DOCTYPE html> declaration is used to inform a website visitor's browser that the document being rendered is an HTML document. While not actually an HTML element itself, every HTML document should being with a DOCTYPE declaration to be compliant with HTML standards.
For HTML5 documents (which nearly all new web documents should be), the DOCTYPE declaration should be:
<!DOCTYPE html>
Show to the browser than the file is a HTML5.
Is followed by the lenguage etiquete according to HTML5 good practiques.
<!doctype html>
<html lang="es">
In this case the second line indicates to the browsers than the file is in example, spanish in this case <html lang="es">
is important for building an HTML documents it is not just HTML but it is an instruction to the web browser about what version of HTML the page is written in.
I know that the DOCTYPE(s) give the browser the list of allowed elements(tags) and attributes.
But i want to know that when you use:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
Will the browser go and download the dtd file or it just a sign that the browsers understand that the type of the HTML is HTML 4(strict).
What about HTML 5 DOCTYPE:
<!DOCTYPE html>
Thank You.
Browsers do not download DTD files. There is no prohibition, but they just don’t use DTDs at all, and they are not required at all. The doctype declarations matter only as “magic strings”, which trigger standards, almost standars, or quirks mode in the browser; this is based solely on the string as such, without accessing any DTD file.
The doctype declarations are a holdover from the time when HTML was defined nominally as an application of SGML – something that was never implemented. An SGML processor is allowed to read a DTD and perform validation against it; it will then be called a validating SGML processor. But browsers never did that. Instead, HTML authors may use separate validators (which only validate, without displaying the document at all).
The doctype declarations have been kept because browser vendors once decided to use the presence or absence of such declarations, and their exact form (as strings), when deciding whether the document should be rendered in “standards mode” or “quirks mode”. HTML5 follows this tradition, although in HTML5, it’s not even nominally a declaration of any kind, just a “doctype string”.
From: http://www.w3schools.com/tags/tag_doctype.asp
The < !DOCTYPE > declaration is not an HTML tag; it is an instruction to
the web browser about what version of HTML the page is written in.
In HTML 4.01, the < !DOCTYPE > declaration refers to a DTD, because HTML
4.01 was based on SGML. The DTD specifies the rules for the markup language, so that the browsers render the content correctly.
HTML5 is not based on SGML, and therefore does not require a reference
to a DTD.
Tip: Always add the < !DOCTYPE > declaration to your HTML documents, so that the browser knows what type of document to expect.
Does the bold statement mean that when we are using HTML 5 we don't need to specify < !DOCTYPE html >?
What does that statement exactly mean?
I am currently using < !DOCTYPE html > in my html file with the browser Firefox 4. I removed that declaration but did not see any difference in the rendered output. Does it mean that the problem may occur in old browsers and not in new ones?
The terminology is confusing, but a DTD (document type definition) is only one part of a document type declaration (usually shortened to "doctype"). You should always include a doctype declaration (<!DOCTYPE html> if you use HTML5), but a document type definition identifier is no longer necessary.
To provide a concrete example, this is what a HTML4.01 document type declaration ("doctype") might have looked like:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
The document type definition ("DTD") identifier in the above declaration is this part:
"-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"
That's the part you can leave off for HTML5. "PUBLIC" specifies the DTD's availability, so that should also not be included if there is no DTD.
Does the bold statement mean that when we are using HTML 5 we don't need to specify ?
It means that you can't specify.
The HTML 5 Doctype has no public or system identifier in it.
I am currently using <!DOCTYPE html> in my html file
That is required. Keep doing that.
with the browser Firefox 4.
The current stable version of Firefox is version 20. You should probably upgrade.
I removed that declaration but did not see any difference in the rendered output. Does it mean that the problem may occur in old browsers and not in new ones?
No, it just means that you don't have any code that is impacted by being in Quirks mode (or that you do but didn't spot the changes).
Lets take a look at the W3C HTML5 definition, they have a conveniënt page about the differences HTML5 brings:
http://www.w3.org/TR/html5-diff/#doctype
2.2 The Doctype
The HTML syntax of HTML5 requires a doctype to be specified to ensure
that the browser renders the page in standards mode. The doctype has
no other purpose. [DOCTYPE]
The doctype declaration for the HTML syntax is and is
case-insensitive. Doctypes from earlier versions of HTML were longer
because the HTML language was SGML-based and therefore required a
reference to a DTD. With HTML5 this is no longer the case and the
doctype is only needed to enable standards mode for documents written
using the HTML syntax. Browsers already do this for .
To support legacy markup generators that cannot generate the preferred
short doctype, the doctype is allowed in the HTML syntax.
The strict doctypes for HTML 4.0, HTML 4.01, XHTML 1.0 as well as
XHTML 1.1 are also allowed (but are discouraged) in the HTML syntax.
In the XML syntax, any doctype declaration may be used, or it may be
omitted altogether. Documents with an XML media type are always
handled in standards mode.
On that page, chapter 1 (Introduction) says more about HTML versus XML syntax:
The HTML5 draft (..) defines a single language called HTML which can be written in HTML syntax and in XML syntax.
So, if your HTML5 is strict XML syntax, i can conclude from the last paragraph that yes in this case you should not prefix a doctype line.
See chapter 2 for the difference in syntax:
HTML5 HTML syntax:
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>Example document</title>
</head>
<body>
<p>Example paragraph</p>
</body>
</html>
HTML5 XML syntax:
<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example document</title>
</head>
<body>
<p>Example paragraph</p>
</body>
</html>
There is some subtle differences in syntax.
If a HTML document has two doctypes, how will the doctypes affect the rendering of the page and which doctype would the browser pick? Is having two (or more) doctypes in a single document valid or confusing?
Example:
<!DOCTYPE html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
</html>
Only a single doctype declaration is permitted. This follows rather directly from the HTML specifications as well the HTML5 drafts, and it can also be checked using a validator.
Thus, there is no specification of what should happen. The natural expectation is that since browsers process the doctype declaration only in “doctype sniffing” when deciding on the browser mode (Quirks Mode vs. Standards Mode), only the first doctype declaration takes effect and the other is ignored.
This can be tested e.g. as follows (using an HTML 3.2 doctype, which triggers Quirks Mode on all doctype-sniffer browsers):
<!DOCTYPE HTML>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<title>Testing duplicate doctype effect</title>
<script>
document.write(document.compatMode);
</script>
</html>
This displays “CSS1Compat” (= Standards Mode), whereas swapping the doctype declarations causes “BackCompat” (= Quirks Mode).
I believe the very first DOCTYPE is used by the browser and it's against the specification to have more than one in a document.
I think (not sure) that the only situation when multiple DOCTYPE-s may be valid is when using IE conditional comments. Browsers other than IE won't see those, of course.
I remember reading a blog entry (can't find it now, so I may be wrong in this) but some (most?) browsers even ignore the DOCTYPE if it's not the first thing they encounter. (This may have been a bug that got fixed since.)
Here's W3School's reference page about DOCTYPE:
http://www.w3schools.com/tags/tag_doctype.asp
If you have multiple DOCTYPE-s in your HTML page then browser will consider first one, browser parse the DOM line by line. Once browser get DOCTYPE then it will stop looking for other doctypes and will jump to search for HTML tag.
In the above question HTML-5 DOCTYPE is mentioned first and then
HTML-4, according to this browser will render things as HTML-5 doctype
It is better to try once in http://www.w3schools.com/ ... Try to use 'code' or 'kbd' or 'dfn' or 'samp' or 'strong' tag by mentioning both doctypes by priority.
What does this tag do?
<!doctype html>
I can see that with this tag on top, my HTML behaves in another way than without.
How do I know if I need this tag?
It's an integral part of HTML as defined in the specification:
8.1.1 The DOCTYPE
A DOCTYPE is a required preamble.
DOCTYPEs are required for legacy reasons. When omitted, browsers tend to use a different rendering mode that is incompatible with some specifications. Including the DOCTYPE in a document ensures that the browser makes a best-effort attempt at following the relevant specifications.
Edit to add:
What does this seatbelt do?
What I can see is that, with this seatbelt on, my car behaves the same way as without. How do I know if I need this seatbelt?
You wont know if you'll need it until something goes wrong and you don't have it.
DOCTYPE Declaration is the abbreviation for Document Type Declaration (DTD).
The DOCTYPE Declaration (DTD or Document Type Declaration) does a couple of things:
When performing HTML validation testing on a web page it tells the HTML (HyperText Markup Language) validator which version of (X)HTML standard the web page coding is supposed to comply with. When you validate your web page the HTML validator checks the coding against the applicable standard then reports which portions of the coding do not pass HTML validation (are not compliant).
It tells the browser how to render the page in standards compliant mode.
If the web page coding does not include a DOCTYPE Declaration (DTD or Document Type Declaration) or it is done incorrectly:
You will not be able to use a HTML (HyperText Markup Language) Validator to check the page coding. HTML validation requires the DOCTYPE declaration.
The browser rendering the webpage will process the coding in Quirks Mode.
The stylesheet may not be implemented as planned.
Which DOCTYPE should you use?
If you are a beginner to HTML (HyperText Markup Language) then I would suggest you use the HTML 4.01 Transitional declaration. It is much more forgiving for the beginner when performing HTML validation. You would also use this declaration if you know that your audience will not have a browser that supports CSS (Cascading Style Sheets).
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
This DOCTYPE declaration still allows elements and presentation attributes that should be in the stylesheet.
If you want to learn to code in preparation for the future but still not ready for XHTML then you would use the Strict declaration.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
With this declaration all presentation attributes are moved to the stylesheet.
A complete list of DOCTYPE Declarations (DTDs) is available at List of valid DTDs you can use in your document.
The doctype declaration should be the very first thing in an HTML
document, before the tag.
The doctype declaration is not an HTML tag; it is an instruction to
the web browser about what version of the markup language the page is
written in.
The doctype declaration refers to a Document Type Definition (DTD).
The DTD specifies the rules for the markup language, so that the
browsers render the content correctly.
Quote from here: http://www.w3schools.com/tags/tag_doctype.asp
:)
A Doctype declaration triggers standards mode in your browser and should always be used. Quirks mode should always be avoided.
Browser war and two modes
To understand the significance of DOCTYPE, let us dig into some history starting from the days of browser wars. During those days web pages were written in two different versions to support both Internet Explorer and Netscape Navigator.
But then W3C took over defining Web standards. But sadly, browsers with new standards were not able to render web pages built for legacy browsers. So, to support the website built for legacy browsers quirks mode was introduced. In which the browser assumes you’ve written old-fashioned, invalid markup and code per the depressing industry norms of the late 1990s.
To differentiate those website from the new ones, DOCTYPE was added, which gave the browser a signal that this web page should be rendered in standards mode.
HTML5 and HTML 4.01
Prior to HTML5, the HTML was SGML-based which required a document type definition (DTD) to establish rules and grammar for markup. Thus, doctype had other information about the document type definition (DTD).
However, with introduction of HTML5 the DOCTYPE is the only thing needed to enable the standards mode.
To make it simple: <!DOCTYPE HTML> states that the code is HTML.