search
HomeWeb Front-endHTML TutorialAbout the use and instructions of DOCTYPE
About the use and instructions of DOCTYPEApr 05, 2017 am 10:19 AM
doctypeuseaboutillustrate

DOCTYPE is not scary, but taking it away will make you scared again and again.

I found that many friends raised questions about p+CSS typesetting and compatibility issues between IE and FF. I asked all questions, but the result is one - the display is strange and difficult to adjust. Most websites we browse, or when we use Dreamweaver to create a new web document, there will be a DocType declaration at the top of the source code. However, many people do not pay attention to it, and even delete it directly during creation. In fact, this is often the beginning of a nightmare. . DOCTYPE is a required element in any web document that adheres to standards. It affects code validation and determines how browsers ultimately display your web documents. In order to avoid the recurrence of DOCTYPE problems, I compiled this document based on the information on hand for reference by myself and interested friends.

By default, the interpretation standards of FF and IE are different. That is to say, if a web page does not declare a DOCTYPE, it will interpret the following HTML with the default DOCTYPE. Under the same standard, the interpretation models of different browsers are different. If the declaration standards are different, I don't need to tell you, just think about it yourself. Learn web standards and browser compatibility. You decide where to start. However, please know the DOCTYPE:

1. What is DOCTYPE

DOCTYPE is the abbreviation of Document Type. In the page, it is used to specify the version of XHTML (or HTML) used by the page. To create a standards-compliant page, an essential and key component is the DOCTYPE declaration. Only by determining a correct DOCTYPE can the logo and CSS in XHTML take effect normally.

2. Rules of DOCTYPE

The DOCTYPE declaration follows certain rules and indicates what set of rules the reading program should use to interpret the markup in the document. In the case of Web documents, the "reader" is usually a program such as a browser or a validator, and the "rules" are the rules contained in a document type definition (dtd) published by the W3C.
Each DTD includes tags, attributes, properties, etc., which are used to mark the content of web documents; it also includes rules that specify which tags can appear in which other tags. Each web recommendation standard (such as HTML 4 Frameset and XHTML 1.0 Transitional) has its own DTD.

Here are the rules taken from the manual:

grammar:

HTML Top Element Availability "Registration//Organization//Type Tag//Definition Language""URL"

Possible values:

- Top-level element: Specifies the type of top-level element declared in the DTD. This corresponds to the declared SGML document type. HTML default. HTML.
- Availability: Specifies whether the Formal Public Identifier (FPI) is a publicly accessible object or a system resource. PUBLIC Default. Publicly accessible objects. SYSTEM System resources, such as local files or URLs.
- Registration: Specifies whether the organization is registered by the International Organization for Standardization (ISO). + Default. The organization name has been registered.
- The organization name is not registered. The Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C) are not registered ISO organizations.
Organization: Specify the name, or OwnerID, of the group or organization responsible for the creation and maintenance of the DTD referenced by the !DOCTYPE declaration. IETF IETF. W3C W3C.
- Type: Specifies the public text class, that is, the type of object being referenced. DTD default. DTD.
- Tag: Specifies a public text description, a unique, descriptive name for the public text being referenced. A version number can be attached at the end. HTML default. HTML.
- Definition: Specify the document type definition.
Frameset Frameset document.
Strict excludes all representative attributes and elements that W3C experts want to phase out because the style sheet is already well established.
Transitional contains all contents except frameSet elements.
- Language: Specifies the public text language, the natural language encoding system used to create the referenced object. The language definition has been written as an ISO 639 language code (uppercase two letters). EN default. English.
- URL: Specifies the location of the referenced object

In order to get a correct DOCTYPE declaration, the key is to make the dtd correspond to the standard that the document follows. For example, assuming that the document follows the xhtml 1.0 strict standard, the document's doctype declaration should reference the corresponding dtd. On the other hand, if the doctype declaration specifies an xhtml dtd, but the document contains old-style html markup, it is inappropriate; similarly, if the doctype declaration specifies an html dtd, but the document contains xhtml 1.0 strict markup , is also inappropriate.

3. What kind of DOCTYPE to choose

As shown in the above example, there are three types of DTD (Document Type Definition) declarations to choose from in XHTML 1.0: Transitional, Strict and Frameset. They are introduced here as follows.

1. transitional

A DTD with less stringent requirements that allows the use of HTML4.01 logos in pages (complying with xhtml syntax standards). The transitional DTD is written as follows:

br/> "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

2. strict

A strict DTD that does not allow the use of any presentation layer identifiers and attributes, such as
, etc. The strict DTD is written as follows:

br/> "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

3. Frame

A DTD specifically used for frame pages. This DTD is used when the page contains frame elements. The DTD of the framework is written as follows:

br/> "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">

Using strict DTD to create pages is of course the most ideal way. However, for web designers who do not have a deep understanding of web standards, it is more appropriate to use a transitional DTD. Because this DTD also allows the use of presentation layer identifiers, elements and attributes, it is more suitable for most web page developers.

4. Issues that need attention

There's nothing special, except that the DOCTYPE declaration must be placed at the top of the XHTML document. Even multiple HTML comment tags above it will not work.

It is best to add DOCTYPE to the sample code, otherwise the effect will be different.

5. Various DOCTYPE

HTML Strict
HTML Transitional
HTML Frameset
XHTML 1.0 Strict
XHTML 1.0 Transitional
XHTML 1.0 Frameset
XHTML 1.1
XHTML 2.0

The above is the detailed content of About the use and instructions of DOCTYPE. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
如何在Go中使用命名管道?如何在Go中使用命名管道?May 11, 2023 pm 04:22 PM

命名管道是一种在操作系统中相对比较低级的进程通信方式,它是一种以文件为中介的进程通信方式。在Go语言中,通过os包提供了对命名管道的支持。在本文中,我们将介绍如何在Go中使用命名管道来实现进程间通信。一、命名管道的概念命名管道是一种特殊的文件,可以被多个进程同时访问。在Linux系统中,命名管道是一种特殊的文件类型,它们存在于文件系统的某个位置上,并且可以在

如何在Go中使用第三方库?如何在Go中使用第三方库?May 11, 2023 pm 03:30 PM

在Go语言中,使用第三方库是非常方便的。许多优秀的第三方库和框架可以帮助我们快速地开发应用程序,同时也减少了我们自己编写代码的工作量。但是如何正确地使用第三方库,确保其稳定性和可靠性,是我们必须了解的一个问题。本文将从以下几个方面介绍如何使用第三方库,并结合具体例子进行讲解。一、第三方库的获取Go语言中获取第三方库有以下两种方式:1.使用goget命令首先

如何在PHP中使用协程?如何在PHP中使用协程?May 12, 2023 am 08:10 AM

随着传统的多线程模型在高并发场景下的性能瓶颈,协程成为了PHP编程领域的热门话题。协程是一种轻量级的线程,能够在单线程中实现多任务的并发执行。在PHP的语言生态中,协程得到了广泛的应用,比如Swoole、Workerman等框架就提供了对协程的支持。那么,如何在PHP中使用协程呢?本文将介绍一些基本的使用方法以及常见的注意事项,帮助读者了解协程的运作原理,以

doctype html 什么意思doctype html 什么意思Mar 06, 2023 pm 02:56 PM

“doctype html”是指html5标准网页声明,即告诉浏览器当前HTML是用第五版本编写的,完整语法“<!DOCTYPE HTML>”。doctype声明是一条指令,必须位于HTML5文档中的第一行,也就是位于“<html>”标签之前。

如何在Go中使用音频处理?如何在Go中使用音频处理?May 11, 2023 pm 04:37 PM

随着音频处理在各种应用场景中的普及,越来越多的程序员开始使用Go编写音频处理程序。Go语言作为一种现代化的编程语言,具有优秀的并发性和高效率的特点,使用它进行音频处理十分方便。本文将介绍如何在Go中使用音频处理技术,包括读取、写入、处理和分析音频数据等方面的内容。一、读取音频数据在Go中读取音频数据有多种方式。其中比较常用的是使用第三方库进行读取,比如go-

如何在 Windows 11 中按需使用 OneDrive 的文件如何在 Windows 11 中按需使用 OneDrive 的文件Apr 14, 2023 pm 12:34 PM

&lt;p&gt;Windows 系统上的 OneDrive 应用程序允许您将文件存储在高达 5 GB 的云上。OneDrive 应用程序中还有另一个功能,它允许用户选择一个选项,是将文件保留在系统空间上还是在线提供,而不占用您的系统存储空间。此功能称为按需文件。在这篇文章中,我们进一步探索了此功能,并解释了有关如何在 Windows 11 电脑上的 OneDrive 中按需使用文件的各种选项。&lt;/p&gt;&lt;h2&gt;如何使用 On

如何在Go中使用嵌套结构?如何在Go中使用嵌套结构?May 11, 2023 pm 04:39 PM

在Go语言中,嵌套结构是一种非常常见的技术。通过将一个结构体嵌入到另一个结构体中,我们可以将复杂的数据模型分解成更小的部分,使其易于理解和维护。本篇文章将介绍如何在Go中使用嵌套结构以及一些最佳实践。一、定义嵌套结构首先,我们需要定义一个包含嵌套结构的结构体。下面的代码演示了如何定义一个包含Person结构体的Company结构体:typePersons

如何在Go中使用WebSocket?如何在Go中使用WebSocket?May 11, 2023 pm 04:17 PM

近年来,WebSocket技术已经成为了Web开发中不可或缺的一部分。WebSocket是一种在单个TCP连接上进行全双工通信的协议,它使得客户端和服务器之间的通信更加流畅和高效。如今,很多现代的Web应用程序都使用了WebSocket技术,例如实时聊天、在线游戏以及实时数据可视化等。Go语言作为一个现代的编程语言,自然也提供了很好的支持WebSock

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Atom editor mac version download

Atom editor mac version download

The most popular open source editor

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.