title: Is it possible to make up HTML Tags?
body: <p>What's stopping me from doing this:</p>
  
  <pre><code>&lt;head&gt;    
  &lt;style type="text/css"&gt;
  red{
      display:block;
      background:red;
      height:20px;
      width:20px;
  }
  &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;red&gt;&lt;/red&gt;
  </code></pre>
  
  <p>Will this work? What's going to stop it? </p>
  
  <p>From what I understand, the browser will find the and match the css styles based on the selector rules, and so long as you specify ALL the required rules (I'm sure there're more), what's stopping me from seeing a small red box on screen?</p>