LordAro/base.css

## base.css
html {
	background-color: #AB9C7D;
	color: black;
	font-family: "Trebuchet MS", Arial, Verdana, Sans-Serif;
	font-size: 12px;
}

body {
	width: 800px;
	margin: auto auto;
}

header {
	background-clip: padding-box;
	overflow: hidden;
	margin-bottom: 20px;

	background: url('/static/img/header-bg.png') repeat;
	border-radius: 0px 0px 5px 5px;
	box-shadow: 0px 0px 3px 2px #444;
	color: #DDDDDD;
}

#openttd-logo {
	margin: 10px;
	text-align: right;
}

nav {
	text-align: center;
	background-color: #444;
}

nav ul {
	display: flex;
	flex-direction: row;
	flex-wrap: nowrap;
	justify-content: space-evenly;
	padding: 0px;
	margin: auto 5px;
	list-style: none;

	min-height: 32px;
}

nav ul li {
	flex-grow: 1;
	line-height: 32px;
}

nav ul li a {
	display: block;

	text-decoration: none;
	color: #DDD;
}

#nav-selected a {
	background: linear-gradient(#FCD085, #FEB439);
	color: #444;
}

main, footer {
	padding: 0.1px; /* Prevents margin collapse */
	margin: 20px auto;
	background-color: white;
	border-radius: 5px 5px;
	box-shadow: 0px 0px 3px 2px #444;
}

main > * {
	margin: 5px;
}

section h1 {
	margin-top: 0px;
}

section div {
	border-top: 1px solid #EEE;
	padding: 20px;

	text-align: justify;
	font-size: 14px;
}

#content-bottom {
	margin: 10px;
	font-size: 11px;
	line-height: 32px;
}

#content-bottom:after {
  content: "";
  display: table;
  clear: both;
}

#content-bottom-links {
	float: left;
}

#content-bottom-links a {
	color: #DD6600;
}

#content-bottom-copyright {
	float: right;
}

h1 {
	line-height: 38px;
	background-image: url('/static/img/section-news.gif'), url('/static/img/section-bg.png');
	background-repeat: no-repeat, no-repeat;
	background-position: left, left;
	padding-left: 28px;

	font-size: 18px;
	color: #365800;
	font-weight: normal;
}

hr {
	margin: auto;
	color: #777;
}

## base.html
<!doctype html>
<html>
<head>
  <title>OpenTTD{% if title is defined %} - {{ title }}{% endif %}</title>

  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <meta name="Description" content="An open source simulator based on the classic game Transport Tycoon Deluxe. It attempts to mimic the original game as closely as possible while extending it with new features." />
  <meta name="Keywords" content="Transport,Tycoon,Deluxe,TTDLX,TTD,OpenTTD,OTTD" />
  <link rel="icon" href="{{ url_for('static', filename='favicon.ico') }}" type="image/icon" />
  <link rel="stylesheet" href="{{ url_for('static', filename='css/base.css') }}" type="text/css" />

  {% block head %}{% endblock %}
</head>
<body>
  <header>
    {% block header %}{% include "header.html" %}{% endblock %}
    <nav>
      {% block nav %}
      {% set navigation_bar = [
        (url_for('index'),               'Home'),
        (url_for('about'),               'About'),
        ('//wiki.openttd.org',           'Manual'),
        ('screenshots',                  'Screenshots'),
        ('servers',                      'Servers'),
        ('development',                  'Development'),
        ('//forum.openttd.org',          'Forum'),
        ('//wiki.openttd.org/Community', 'Community'),
        ('contact',                      'Contact'),
        ('donate',                       'Donate'),
      ] -%}
      <ul>
        {% for url, caption in navigation_bar %}
        <li {% if url == request.path %}id="nav-selected"{% endif %}>
          <a href="{{ url }}">{{ caption }}</a>
        </li>
        {% endfor %}
      </ul>
      {% endblock %}
    </nav>
  </header>
  <main>
    {% block main %}
    <section>
    <h1>This is a section header</h1>
    <div>
    <p>
OpenTTD is an open source simulation game based upon the popular Microprose game "Transport Tycoon Deluxe", written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features.
</p>

<p>
OpenTTD is licensed under the GNU General Public License version 2.0. For more information, see the file COPYING included with every release and source download of the game.
    </p>
    </div>
    </section>
    {% endblock %}
    <div id="content-bottom">
    <hr />
    <span id="content-bottom-links">
      <a href="#">Privacy policy</a> |
      <a href="#">Login</a> |
      <a href="{{ url_for('contact') }}">Contact</a>
    </span>
    <span id="content-bottom-copyright">
      Copyright &copy; 2005-2017 OpenTTD Team
    </span>
    </div>
  </main>
  <footer>
    {% block footer %}This is a footer{% include "footer.html" %}{% endblock %}
  </footer>
</body>
</html>
	html {
	background-color: #AB9C7D;
	color: black;
	font-family: "Trebuchet MS", Arial, Verdana, Sans-Serif;
	font-size: 12px;
	}

	body {
	width: 800px;
	margin: auto auto;
	}

	header {
	background-clip: padding-box;
	overflow: hidden;
	margin-bottom: 20px;

	background: url('/static/img/header-bg.png') repeat;
	border-radius: 0px 0px 5px 5px;
	box-shadow: 0px 0px 3px 2px #444;
	color: #DDDDDD;
	}

	#openttd-logo {
	margin: 10px;
	text-align: right;
	}

	nav {
	text-align: center;
	background-color: #444;
	}

	nav ul {
	display: flex;
	flex-direction: row;
	flex-wrap: nowrap;
	justify-content: space-evenly;
	padding: 0px;
	margin: auto 5px;
	list-style: none;

	min-height: 32px;
	}

	nav ul li {
	flex-grow: 1;
	line-height: 32px;
	}

	nav ul li a {
	display: block;

	text-decoration: none;
	color: #DDD;
	}

	#nav-selected a {
	background: linear-gradient(#FCD085, #FEB439);
	color: #444;
	}

	main, footer {
	padding: 0.1px; /* Prevents margin collapse */
	margin: 20px auto;
	background-color: white;
	border-radius: 5px 5px;
	box-shadow: 0px 0px 3px 2px #444;
	}

	main > * {
	margin: 5px;
	}

	section h1 {
	margin-top: 0px;
	}

	section div {
	border-top: 1px solid #EEE;
	padding: 20px;

	text-align: justify;
	font-size: 14px;
	}

	#content-bottom {
	margin: 10px;
	font-size: 11px;
	line-height: 32px;
	}

	#content-bottom:after {
	content: "";
	display: table;
	clear: both;
	}

	#content-bottom-links {
	float: left;
	}

	#content-bottom-links a {
	color: #DD6600;
	}

	#content-bottom-copyright {
	float: right;
	}

	h1 {
	line-height: 38px;
	background-image: url('/static/img/section-news.gif'), url('/static/img/section-bg.png');
	background-repeat: no-repeat, no-repeat;
	background-position: left, left;
	padding-left: 28px;

	font-size: 18px;
	color: #365800;
	font-weight: normal;
	}

	hr {
	margin: auto;
	color: #777;
	}
	<!doctype html>
	<html>
	<head>
	<title>OpenTTD{% if title is defined %} - {{ title }}{% endif %}</title>

	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<meta name="Description" content="An open source simulator based on the classic game Transport Tycoon Deluxe. It attempts to mimic the original game as closely as possible while extending it with new features." />
	<meta name="Keywords" content="Transport,Tycoon,Deluxe,TTDLX,TTD,OpenTTD,OTTD" />
	<link rel="icon" href="{{ url_for('static', filename='favicon.ico') }}" type="image/icon" />
	<link rel="stylesheet" href="{{ url_for('static', filename='css/base.css') }}" type="text/css" />

	{% block head %}{% endblock %}
	</head>
	<body>
	<header>
	{% block header %}{% include "header.html" %}{% endblock %}
	<nav>
	{% block nav %}
	{% set navigation_bar = [
	(url_for('index'), 'Home'),
	(url_for('about'), 'About'),
	('//wiki.openttd.org', 'Manual'),
	('screenshots', 'Screenshots'),
	('servers', 'Servers'),
	('development', 'Development'),
	('//forum.openttd.org', 'Forum'),
	('//wiki.openttd.org/Community', 'Community'),
	('contact', 'Contact'),
	('donate', 'Donate'),
	] -%}
	<ul>
	{% for url, caption in navigation_bar %}
	<li {% if url == request.path %}id="nav-selected"{% endif %}>
	<a href="{{ url }}">{{ caption }}</a>
	</li>
	{% endfor %}
	</ul>
	{% endblock %}
	</nav>
	</header>
	<main>
	{% block main %}
	<section>
	<h1>This is a section header</h1>
	<div>
	<p>
	OpenTTD is an open source simulation game based upon the popular Microprose game "Transport Tycoon Deluxe", written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features.
	</p>

	<p>
	OpenTTD is licensed under the GNU General Public License version 2.0. For more information, see the file COPYING included with every release and source download of the game.
	</p>
	</div>
	</section>
	{% endblock %}
	<div id="content-bottom">
	<hr />
	<span id="content-bottom-links">
	<a href="#">Privacy policy</a> \|
	<a href="#">Login</a> \|
	<a href="{{ url_for('contact') }}">Contact</a>
	</span>
	<span id="content-bottom-copyright">
	Copyright © 2005-2017 OpenTTD Team
	</span>
	</div>
	</main>
	<footer>
	{% block footer %}This is a footer{% include "footer.html" %}{% endblock %}
	</footer>
	</body>
	</html>