<meta>标签提供了 HTML 文档的元数据。元数据不会显示在客户端，但是会被浏览器解析。
META元素通常用于指定网页的描述，关键词，文件的最后修改时间，作者及其他元数据。
元数据可以被使用浏览器（如何显示内容或重新加载页面），搜索引擎（关键词），或其他 Web 服务调用。
每一个html页面都是需要写meta标签的。
页面自动生成代码的时候就会自动生成，不需要自己额外写，除非要补充其他内容。
一、基本属性标签常常被用来定义HTML文档的元数据或者HTTP协议的指向，这些元数据常用在SEO、HTML Pages or Apps on Mobile/Handheld Devices，该标签主要包括以下属性：
Attribute Description
Name Name for the property. Can be anything. Examples include, keywords, description, author, revised, generator etc.
content Specifies the property’s value.
scheme Specifies a scheme to interpret the property’s value (as declared in the content attribute).
http-equiv Used for http response message headers. For example http-equiv can be used to refresh the page or to set a cookie. Values include content-type, expires, refresh and set-cookie.
二、基本的HTML Meta标签
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<!-- SEO -->
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<meta name="keywords" content="your, tags"/>
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<meta name="description" content="150 words"/>
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<meta name="subject" content="your website's subject">
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<meta name="copyright"content="company name">
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<meta name="language" content="ES">
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<meta name="robots" content="index,follow" />
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<meta name="revised" content="Sunday, July 18th, 2010, 5:15 pm" />
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<meta name="abstract" content="">
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<meta name="topic" content="">
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<meta name="summary" content="">
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<meta name="Classification" content="Business">
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<meta name="author" content="name, [email protected]">
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<meta name="designer" content="">
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<meta name="copyright" content="">
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<meta name="reply-to" content="[email protected]">
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<meta name="owner" content="">
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<meta name="url" content="http://www.websiteaddrress.com">
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<meta name="identifier-URL" content="http://www.websiteaddress.com">
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<meta name="directory" content="submission">
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<meta name="category" content="">
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<meta name="coverage" content="Worldwide">
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<meta name="distribution" content="Global">
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<meta name="rating" content="General">
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<meta name="revisit-after" content="7 days">
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<meta http-equiv="Expires" content="0">
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<meta http-equiv="Pragma" content="no-cache">
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<meta http-equiv="Cache-Control" content="no-cache">
三、OpenGraph Meta标签
为了提高站外内容的传播效率，2010年9月，在F8会议上Facebook公布了一套开放图景协议(Open Graph Protocol)，任何网页只要遵守该协议，SNS就能从页面上提取最有效的信息并呈现给用户。通过Open Graph把其他社交网站建构的网络给连接起来，将创造一个更聪明、更与社交连接、更个人化也更具语意意识的网络。
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<meta name="og:title" content="The Rock"/>
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<meta name="og:type" content="movie"/>
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<meta name="og:url" content="http://www.imdb.com/title/tt0117500/"/>
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<meta name="og:image" content="http://ia.media-imdb.com/rock.jpg"/>
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<meta name="og:site_name" content="IMDb"/>
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<meta name="og:description" content="A group of U.S. Marines, under command of..."/>
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<meta name="fb:page_id" content="43929265776" />
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<meta name="og:email" content="[email protected]"/>
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<meta name="og:phone_number" content="650-123-4567"/>
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<meta name="og:fax_number" content="+1-415-123-4567"/>
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<meta name="og:latitude" content="37.416343"/>
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<meta name="og:longitude" content="-122.153013"/>
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<meta name="og:street-address" content="1601 S California Ave"/>
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<meta name="og:locality" content="Palo Alto"/>
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<meta name="og:region" content="CA"/>
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<meta name="og:postal-code" content="94304"/>
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<meta name="og:country-name" content="USA"/>
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<meta property="og:type" content="game.achievement"/>
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<meta property="og:points" content="POINTS_FOR_ACHIEVEMENT"/>
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<meta property="og:video" content="http://example.com/awesome.swf" />
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<meta property="og:video:height" content="640" />
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<meta property="og:video:width" content="385" />
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<meta property="og:video:type" content="application/x-shockwave-flash" />
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<meta property="og:video" content="http://example.com/html5.mp4" />
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<meta property="og:video:type" content="video/mp4" />
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<meta property="og:video" content="http://example.com/fallback.vid" />
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<meta property="og:video:type" content="text/html" />
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<meta property="og:audio" content="http://example.com/amazing.mp3" />
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<meta property="og:audio:title" content="Amazing Song" />
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<meta property="og:audio:artist" content="Amazing Band" />
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<meta property="og:audio:album" content="Amazing Album" />
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<meta property="og:audio:type" content="application/mp3" />
四、公司/服务 Meta标签
4.1 CLAIMID
ClaimID was a website that allowed users to create unique profiles that showed personal websites, profiles at other sites, and other biographical information.
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<meta name="microid" content="mailto+http:sha1:e6058ed7fca4a1921cq91d7f1f3b8736cd3cc1g7" />
4.2 APPLE META TAGS
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<!-- 从桌面icon启动IOS Safari是否进入全屏状态（APP模式） -->
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<meta name="apple-mobile-web-app-capable" content="yes">
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<!-- 添加到主屏幕“后，全屏显示 -->
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<meta name="apple-touch-fullscreen" content="yes" >
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<!-- 指定状态栏的颜色 -->
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<meta name="apple-mobile-web-app-status-bar-style" content="black">
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<!-- ios设备上禁止将数字识别为可点击的telephone link -->
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<meta name="format-detection" content="telephone=no">
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<!-- 页面CSS计算时使用宽度为320，初始缩放比例2.3， 不允许用户缩放, 最大缩放因子为1 -->
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<meta name="viewport" content="width = 320, initial-scale = 2.3, user-scalable = no, maximum-scale=1 ">
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<!-- 页面CSS计算时使用的宽度根据设备给定值自适应 -->
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<meta name= "viewport" content = "width = device-width">
4.3 INTERNET EXPLORER META TAGS
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<meta http-equiv="Page-Enter" content="RevealTrans(Duration=2.0,Transition=2)" />
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<meta http-equiv="Page-Exit" content="RevealTrans(Duration=3.0,Transition=12)" />
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<meta name="mssmarttagspreventparsing" content="true">
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<!-- 告诉IE浏览器以什么模式展示网页 -->
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<meta http-equiv="X-UA-Compatible" content="chrome=1">
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<meta name="msapplication-starturl" content="http://blog.reybango.com/about/"/>
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<meta name="msapplication-window" content="width=800height=600"/>
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<meta name="msapplication-navbutton-color" content="red"/>
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<meta name="application-name" content="Rey Bango Front-end Developer"/>
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<meta name="msapplication-tooltip" content="Launch Rey Bango's Blog"/>
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<meta name="msapplication-task" content="name=Aboutaction-uri=/about/icon-uri=/images/about.ico" />
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<meta name="msapplication-task" content="name=The Big Listaction-uri=/the-big-list-of-javascript-css-and-html-development-tools-libraries-projects-and-books/icon-uri=/images/list_links.ico" />
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<meta name="msapplication-task" content="name=jQuery Postsaction-uri=/category/jquery/icon-uri=/images/jquery.ico" />
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<meta name="msapplication-task" content="name=Start Developingaction-uri=/category/javascript/icon-uri=/images/script.ico" />
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<!-- Tab标签icon -->
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<link rel="shortcut icon" href="/images/favicon.ico" />
4.4 TWEETMEME META TAGS
Tweetmeme跟踪Twitter上的链接，以给用户更好的体验。它使用一种常用的排序系统，以在这个微博世界里找出最热门的信息。
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<meta name="tweetmeme-title" content="Retweet Button Explained" />
4.5 BLOG CATALOG META TAGS
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<meta name="blogcatalog" />
4.6 RAILS META TAGS
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<meta name="csrf-param" content="authenticity_token"/>
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<meta name="csrf-token" content="/bZVwvomkAnwAI1Qd37lFeewvpOIiackk9121fFwWwc="/>
五、创建自定义 Meta标签
Use custom meta tags to store data that you need in javascript, instead of hard-coding that data into your javascript. I store my Google Analytics code in meta tags. Here’s some examples:
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<meta name="google-analytics" content="1-AHFKALJ"/>
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<meta name="disqus" content="EEEE"/>
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<meta name="uservoice" content="XXXX"/>
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<meta name="mixpanel" content="XXXXE"/>
