title: Browser shows plain text instead of HTML in mac
body: <p>I want to write an html document like this :</p>
  
  <pre><code>&lt;html&gt;
  &lt;body&gt;
  
  &lt;h1&gt;My First Heading&lt;/h1&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>I wrote it and saved it in my desktop with the name <code>hello.html</code> , but when I open this file with firefox or safari, the browser shows the whole text (including <code>&lt;html&gt;</code> and all of the texts) instead of only showing <code>my first heading</code>!
  what's the problem?</p>