title: I don't understand the functions of some meta tags
body: <p>I searched about some <code>meta</code> values and attributes&gt; I SEARCHED ON GOOGLE and YOUTUBE but no understandable answer. Most of the videos are in HINDI. I'll type a code which contains all meta-tags which I don't understand them. All what's written I want to know their functions and their possible values and the difference in function between each of the values. I want to know these details about each of the attributes' values. I also want to know if these values and tags are still used in HTML5</p>
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;meta http-equiv="pragma" content="" /&gt; 
  &lt;meta http-equiv="robots" content="" /&gt; 
  &lt;meta http-equiv="expires" content="" /&gt; 
  &lt;meta http-equiv="revised" content="" /&gt; 
  &lt;meta http-equiv="generator" content="" /&gt; </code></pre>
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