title: Incoherent HTML behavior in relation with DOCTYPE
body: <p>This piece of code executes <em>appropriately</em>:</p>
  
  <pre><code>&lt;!-- &lt;!DOCTYPE html&gt; --&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;style&gt;
  #banner
  {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 48px;
  background: black;
  color: white;
  font-size: 24px;
  text-align: center;
  }
  
  #mainTitle
  {
  position: fixed;
  top:48;
  left: 0;
  width: 100%;
  height: 88px;
  font-size: 56px;
  text-align: center;
  background-color: navajowhite;
  text-transform: uppercase;
  color: salmon;
  }
  
  #myBody
  {
  height:600px;
  background-color: yellow;
  }
  
  #mainContainer
  {
  margin: 120px auto;/**/
  width: 975px;
  padding: 30px;
  background-color: pink;
  }
  &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="banner"&gt;My Title&lt;/div&gt;
  &lt;div id="mainTitle"&gt;My main title&lt;/div&gt;
  &lt;div id="mainContainer"&gt;
  &lt;div id="myBody"&gt;Everything here in myBody&lt;/div&gt;
  &lt;/div&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p>Now if you <strong>de-comment-out</strong> the DOCTYPE declaration it executes incoherently (using either Netbeans 8.2 or Smultron 'View' command). This behaviour is thus clearly related to the HTML5 header.</p>
  
  <p>What is the matter, here?</p>
  
  <p>Note: I am sorry this piece of code is not up on Fiddler. Nevertheless it should be very easy to test is 'as is' by pasting it into a new file using Netbeans and invoking the 'View' command.  </p>