HTML从上至下，本篇记录Meta标签的使用。
摘抄一段GitHub HEAD 仓库的代码 很全面地解释说明了Meta用法
<!--
The following 2 meta tags *must* come first in the <head>
to consistently ensure proper document rendering.
Any other head element should come *after* these tags.
-->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!--
Allows control over where resources are loaded from.
Place as early in the <head> as possible, as the tag
only applies to resources that are declared after it.
-->
<meta http-equiv="Content-Security-Policy" content="default-src 'self'">
<!-- Name of web application (only should be used if the website is used as an app) -->
<meta name="application-name" content="Application Name">
<!-- Theme Color for Chrome, Firefox OS and Opera -->
<meta name="theme-color" content="#4285f4">
<!-- Short description of the document (limit to 150 characters) -->
<!-- This content *may* be used as a part of search engine results. -->
<meta name="description" content="A description of the page">
<!-- Control the behavior of search engine crawling and indexing -->
<meta name="robots" content="index,follow"><!-- All Search Engines -->
<meta name="googlebot" content="index,follow"><!-- Google Specific -->
<!-- Tells Google not to show the sitelinks search box -->
<meta name="google" content="nositelinkssearchbox">
<!-- Tells Google not to provide a translation for this document -->
<meta name="google" content="notranslate">
<!-- Verify website ownership -->
<meta name="google-site-verification" content="verification_token"><!-- Google Search Console -->
<meta name="yandex-verification" content="verification_token"><!-- Yandex Webmasters -->
<meta name="msvalidate.01" content="verification_token"><!-- Bing Webmaster Center -->
<meta name="alexaVerifyID" content="verification_token"><!-- Alexa Console -->
<meta name="p:domain_verify" content="code_from_pinterest"><!-- Pinterest Console-->
<meta name="norton-safeweb-site-verification" content="norton_code"><!-- Norton Safe Web -->
<!-- Identify the software used to build the document (i.e. - WordPress, Dreamweaver) -->
<meta name="generator" content="program">
<!-- Short description of your document's subject -->
<meta name="subject" content="your document's subject">
<!-- Gives a general age rating based on the document's content -->
<meta name="rating" content="General">
<!-- Allows control over how referrer information is passed -->
<meta name="referrer" content="no-referrer">
<!-- Disable automatic detection and formatting of possible phone numbers -->
<meta name="format-detection" content="telephone=no">
<!-- Completely opt out of DNS prefetching by setting to "off" -->
<meta http-equiv="x-dns-prefetch-control" content="off">
<!-- Stores a cookie on the client web browser for identification purposes -->
<meta http-equiv="set-cookie" content="name=value; expires=date; path=url">
<!-- Specifies the document to appear in a specific frame -->
<meta http-equiv="Window-Target" content="_value">
<!-- Geo tags -->
<meta name="ICBM" content="latitude, longitude">
<meta name="geo.position" content="latitude;longitude">
<meta name="geo.region" content="country[-state]"><!-- Country code (ISO 3166-1): mandatory, state code (ISO 3166-2): optional; eg. content="US" / content="US-NY" -->
<meta name="geo.placename" content="city/town"><!-- eg. content="New York City" -->
