Meta Tags

Most Used
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<title>relevant and attractive phrase </title>
<meta name="description" content="text">
<meta name="keywords" content="text">

Robots Tag
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<meta name="robots" content="INDEX, FOLLOW">
<meta name="robots" content="index, nofollow">
<meta name="robots" content="noindex, follow">
<meta name="robots" content="noindex, nofollow">
<meta name="ROBOTS" CONTENT="NOARCHIVE">

Search Engine will not store cache
<meta name="GOOGLEBOT" CONTENT="NOSNIPPET"> 

It is not supported by any major search engines (Google, Yahoo!, or Bing)
<meta name="revisit-after" content="after 30 days">

No search engines or web browsers use the copyright meta tag
<meta name="copyright" content="text">


<meta name="googlebot" content="noodp">

<meta name="language" content="english">

<meta name="reply-to" content="email address">

<meta name="web_author" content="text">

<meta http-equiv="name" content="value">

Tell the browser to load the page from the server, not from a browser cache, Date format is (Day, dd Mon yyyy hh:mm:ss GMT)
<meta http-equiv="expires" content="Sun, 28 Nov 2010 13:21:02 GMT">

Source:

http://code.lancepollard.com/complete-list-of-html-meta-tags/

Open Graph Meta Data
http://ogp.me/