About HTML head tag

There are many tags and elements in the HTML head, which involve browser rendering of web pages, SEO, etc. Each browser core and each domestic browser manufacturer have their own tag elements, which results in a lot of differences. In the era of mobile Internet, the head structure and meta elements of mobile terminals are even more important. Understanding the meaning of each tag and writing a head tag that meets your own needs is the purpose of this article. This article is based on Yishi's article and provides an expanded summary to introduce the meaning and usage scenarios of each tag and element in commonly used heads.

DOCTYPE

DOCTYPE (Document Type), this declaration is located at the very beginning of the document, before the html tag. This tag tells the browser which HTML or XHTML specification the document uses.

The DTD (Document Type Definition) declaration starts with and is not case-sensitive. There is no content in front of it. If there is other content (except spaces), the browser will turn on quirks mode under IE to render the web page. Public DTD, the name format is registration // organization // type tag // language, registration refers to whether the organization is registered by the International Organization for Standardization (ISO), + means yes, - means no. Organization is the name of the organization, such as: W3C. The type is usually DTD. A tag specifies a description of the public text, that is, a unique descriptive name for the referenced public text, which can be followed by a version number. The final language is the ISO 639 language identifier of the DTD language, such as: EN for English, ZH for Chinese. XHTML 1.0 can declare three DTD types. Represents strict version, transitional version, and frame-based HTML document respectively.

• HTML 4.01 strict

  nbsp;HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

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• HTML 4.01 Transitional

  nbsp;HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

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• HTML 4.01 Frameset

  nbsp;HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">

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• The latest HTML5 introduces more concise writing, which is forward and backward compatible, and is recommended for use.

  nbsp;html>

doctype has two main purposes in HTML.

• Validate documents.

It tells the user agent and validator what DTD this document is written according to. This action is passive. Every time the page is loaded, the browser does not download the DTD and check the validity. It is only enabled when the page is manually verified.

• Determine the browser's rendering mode

  For practical operations, inform the browser which parsing algorithm to use when reading the document. If it is not written, the browser will parse the code according to its own rules, which may seriously affect the html layout. Browsers have three ways to parse HTML documents.

• Non-weird (standard) mode

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• Weird Mode

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• Some weird (almost standard) modes About IE browser's document mode, browser mode, strict mode, weird mode, DOCTYPE tag, detailed reading mode? standard! Content.

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charset

Declaring the character encoding used in the document,

<meta>

Before html5, the web page would write like this:

<meta>

These two are equivalent. You can read the details step by step: vs , so it is recommended to use the shorter one, which is easier to use. memory.

lang attribute

Simplified Chinese

Traditional Chinese

Why is lang="zh-cmn-Hans" instead of the lang="zh-CN" we usually write? Please read further: Should the statement at the head of the page be lang="zh" or lang="zh-cn ".

Priority is given to using the latest version of IE and Chrome

<meta>

360 Use Google Chrome Frame

<meta>

360 browser will immediately switch to the corresponding speed core after reading this tag. Also, just to be on the safe side, join

<meta>

The effect that can be achieved by writing this way is that if Google Chrome Frame is installed, GCF will be used to render the page. If GCF is not installed, the highest version of the IE kernel will be used for rendering.

Related links: Browser kernel control Meta tag documentation

Baidu prohibits transcoding

When you open a webpage through Baidu mobile phone, Baidu may transcode your webpage, take off your clothes, and put an advertisement for dog skin plaster on your body. To do this, you can add

<meta>

in the head. Related links: SiteApp Transcoding Statement

SEO optimization part

• Page title

• 
  

• Page keywords keywords

  <meta>

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• Page description content description

  <meta>

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• Define web page author author

  <meta>

• 
  

• 定义网页搜索引擎索引方式，robotterms 是一组使用英文逗号「,」分割的值，通常有如下几种取值：none，noindex，nofollow，all，index和follow。

  <meta>

　　相关链接：WEB1038 -

　　标记包含无效的值

　　viewport

　　viewport 可以让布局在移动浏览器上显示的更好。 通常会写

<meta>

　　width=device-width 会导致 iPhone 5 添加到主屏后以 WebApp 全屏模式打开页面时出现黑边(http://bigc.at/ios-webapp-viewport-meta.orz)

　　content 参数：

• width viewport 宽度(数值/device-width)

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• height viewport 高度(数值/device-height)

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• initial-scale 初始缩放比例

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• maximum-scale 最大缩放比例

• 
  

• minimum-scale 最小缩放比例

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• user-scalable 是否允许用户缩放(yes/no)

• 
  

• minimal-ui iOS 7.1 beta 2 中新增属性，可以在页面加载时最小化上下状态栏。这是一个布尔值，可以直接这样写：

  <meta>

　　而如果你的网站不是响应式的，请不要使用 initial-scale 或者禁用缩放。

<meta>

　　相关链接：非响应式设计的viewport

　　适配 iPhone 6 和 iPhone 6plus 则需要写：

<meta>
<meta>

　　大部分 4.7~5 寸的安卓设备的 viewport 宽设为 360px，iPhone 6 上却是 375px，大部分 5.5 寸安卓机器（比如说三星 Note）的 viewport 宽为 400，iPhone 6 plus 上是 414px。

　　ios 设备

　　添加到主屏后的标题（iOS 6 新增）

<meta> 

　　是否启用 WebApp 全屏模式

<meta> 

　　设置状态栏的背景颜色

<meta> 

　　只有在 "apple-mobile-web-app-capable" content="yes" 时生效

　　content 参数：

• default 默认值。

• 
  

• black 状态栏背景是黑色。

• 
  

• black-translucent 状态栏背景是黑色半透明。 如果设置为 default 或 black ,网页内容从状态栏底部开始。 如果设置为 black-translucent ,网页内容充满整个屏幕，顶部会被状态栏遮挡。

　　禁止数字识自动别为电话号码

<meta> 

　　iOS 图标

　　rel 参数： apple-touch-icon 图片自动处理成圆角和高光等效果。 apple-touch-icon-precomposed 禁止系统自动添加效果，直接显示设计原图。 iPhone 和 iTouch，默认 57x57 像素，必须有

<link> <!-- iPhone 和 iTouch，默认 57x57 像素，必须有 -->

　　iPad，72x72 像素，可以没有，但推荐有

<link> <!-- iPad，72x72 像素，可以没有，但推荐有 -->

　　Retina iPhone 和 Retina iTouch，114x114 像素，可以没有，但推荐有

<link> <!-- Retina iPhone 和 Retina iTouch，114x114 像素，可以没有，但推荐有 -->

　　Retina iPad，144x144 像素，可以没有，但推荐有

<link> <!-- Retina iPad，144x144 像素，可以没有，但推荐有 -->

　　IOS 图标大小在iPhone 6 plus上是180×180，iPhone 6 是120x120。 适配iPhone 6 plus，则需要在中加上这段

<link>

　　iOS 启动画面

　　官方文档：https://developer.apple.com/library/ios/qa/qa1686/_index.html 参考文章：http://wxd.ctrip.com/blog/2013/09/ios7-hig-24/

　　iPad 的启动画面是不包括状态栏区域的。

　　iPad 竖屏 768 x 1004（标准分辨率）

<link> 

　　iPad 竖屏 1536x2008（Retina）

<link> 

　　iPad 横屏 1024x748（标准分辨率）

<link> 

　　iPad 横屏 2048x1496（Retina）

<link> 

　　iPhone 和 iPod touch 的启动画面是包含状态栏区域的。

　　iPhone/iPod Touch 竖屏 320x480 (标准分辨率)

<link> 

　　iPhone/iPod Touch 竖屏 640x960 (Retina)

<link> 

　　iPhone 5/iPod Touch 5 竖屏 640x1136 (Retina)

<link> 

　　添加智能 App 广告条 Smart App Banner（iOS 6+ Safari）

<meta> 

　　iPhone 6对应的图片大小是750×1294，iPhone 6 Plus 对应的是1242×2148 。

<link>

<link>

　　Windows 8

　　Windows 8 磁贴颜色

<meta> 

　　Windows 8 磁贴图标

<meta> 

　　rss订阅

<link> 

　　favicon icon

<link> 

　　比较详细的 favicon 介绍可参考https://github.com/audreyr/favicon-cheat-sheet

　　移动端的meta

<meta>
<meta>
<meta>
<meta>
<meta>
<meta>
<meta>
<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

<meta>

　　这是来自 toobug 的分享总结。

　　更多的 meta 标签参考

• COMPLETE LIST OF HTML META TAGS

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• 18 Meta Tags Every Webpage Should Have in 2013

　　参考文章：

• 常用的 HTML 头部标签

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• html5_header

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• amazeui css

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• DOCTYPE

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• 10 new changes in IOS 8 that WEB engineers and designers must learn

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