Functions and declaration methods of the XHTML doctype in W3C standards

Doctype is short for document type. It is used to describe the XHTML or html version you use in web design.
To create a standard web page, the doctype Declaration is an essential part. Your logo and CSS will not take effect unless your XHTML determines a correct doctype.

 

 

Syntax
HTML top-level element availability "Registration/organization/type tag // Definition Language" "url"

The top-level element specifies the type of the top-level element declared in the DTD. This corresponds to the declared SGML document type. HTML default. HTML.

Availability specifies whether the FPI is a publicly accessible object or a system resource. Public default. Publicly accessible objects.
System resources, such as local files or URLs.

Registration specifies whether an organization is registered by the International Standardization Organization (ISO. + Default. The organization name is already registered.
-The organization name is not registered. The Internet Engineering Task Group (IETF) and the World Wide Web Association (W3C) are not registered ISO organizations.

The organization is specified to indicate the owner! Doctype declares the name of the group or organization that creates and maintains the referenced DTD, that is, ownderid. IETF.
W3C.

Type specifies the public text class, that is, the referenced object type. Default DTD. DTD.

The tag specifies the description of the public text, that is, the unique descriptive name of the referenced public text. The version number can be included later. HTML default. HTML.

Define the specified document type definition.

Frameset framework set documentation.
Strict exclude representative attributes and elements that W3C experts want to gradually remove because style sheets are well-developed.
Transitional contains all content except the frameset element.

The language specifies the public text language, that is, the natural language encoding system used to create the referenced object.

The language definition has been written in the ISO 639 language code (two uppercase letters ). En by default. English.

The URL specifies the location of the referenced object.
 

Doctype declaration and usage suggestions in W3C standards
Strictly standard HTML 4.01 (HTML 4.01 strict)
This DTD contains all HTML elements and attributes, but does not include outdated elements (such as fonts), and the framework is not allowed.

<! Doctype HTML public "-// W3C // dtd html 4.01 // en"

Http://www.w3.org/tr/html4/strict.dtd>

 

Transitional HTML 4.01 (HTML 4.01 transitional)
This DTD contains all HTML elements and attributes. Contains obsolete elements (such as fonts ). However, the framework is not allowed.

<! Doctype HTML public "-// W3C // dtd html 4.01 transitional // en"

Http://www.w3.org/tr/html4/loose.dtd>

 

HTML 4.01 of the Integrated Framework (HTML 4.01 frameset)
This DTD is basically the same as the transitional HTML 4.01, but the framework is allowed.

<! Doctype HTML public "-// W3C // dtd html 4.01 frameset // en"

Http://www.w3.org/tr/html4/frameset.dtd>

 

Strict XHTML 1.0 (XHTML 1.0 strict)
This DTD contains all HTML elements and attributes, but does not include outdated elements (such as fonts). The framework is not allowed. In addition, the entire document must comply with XML standards.

<! Doctype HTML public "-// W3C // dtd xhtml 1.0 strict // en"

Http://www.w3.org/tr/xhtml1/dtd/xhtml1-strict.dtd>

 

Transitional XHTML 1.0 (XHTML 1.0 transitional)
This DTD contains all HTML elements and attributes. Contains obsolete elements (such as fonts ). However, the framework is not allowed. The entire document must comply with XML standards.

<! Doctype HTML public "-// W3C // dtd xhtml 1.0 transitional // en"

Http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd>

 

XHTML 1.0 (XHTML 1.0 frameset) of the integration framework)
This DTD is basically the same as the transitional xhtml1.0, but the framework is allowed. The entire document must comply with XML standards.

<! Doctype HTML public "-// W3C // dtd xhtml 1.0 frameset // en"

Http://www.w3.org/tr/xhtml1/dtd/xhtml1-frameset.dtd>

 

Xhtml1.1
This DTD is basically the same as the strict XHTML, but some custom tags can be added.

 

<! Doctype HTML public "-// W3C // dtd xhtml 1.1 // en"

Http://www.w3.org/tr/xhtml11/dtd/xhtml11.dtd>