CSS doesn't work on Firefox
<p>This is the HTML code, i don't know if i'm making a mistake in those &lt; link/></p>

<pre><code>&lt;! DOCTYPE html&gt;
&lt;html lang="es"&gt;
  &lt;head&gt;
    &lt;title&gt;Appicua&lt;/title&gt;
    &lt;link href="C:/Users/DAVID NEGRETE/Desktop/Portal web - Base code/portalWebStyle.css" rel="stylesheet" type="text/css" /&gt;
    &lt;link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous"&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div class="test"&gt;&lt;/div&gt;
    &lt;script src="C:/Users/DAVID NEGRETE/Desktop/web/js/jquery.js" type="text/javascript"&gt;&lt;/script&gt;
    &lt;script src="C:/Users/DAVID NEGRETE/Desktop/Portal web - Base code/portalWebExt.js" type="text/javascript" &lt;/script&gt;
    &lt;script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" crossorigin="anonymous"&gt;&lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt; 
</code></pre>

<p>And now this is the CSS code:</p>

<pre><code>.test{
  width:50px;
  height:50px;
  background-color:red;
  border-color:black;
  border-width:5px;
  border-style:solid;
  margin:5%;
}
</code></pre>

<p>As you can see is a simple red square, the problem is that all this code works perfect on Google Chrome and Internet Explorer, but on Firefox it's not even displayed on the screen.</p>

<p>Why is that happening?</p>