_includes/head.html

<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>{% if page.title %}{{ page.title | escape }}{% else %}{{ site.title | escape }}{% endif %}</title>
  <meta name="description" content="{% if page.excerpt %}{{ page.excerpt | strip_html | strip_newlines | truncate: 160 }}{% else %}{{ site.description }}{% endif %}">
  <link rel="stylesheet" href="{{ "/css/main.css" | prepend: site.baseurl | prepend: site.url}}">
  <link rel="stylesheet" href="{{ "/css/syntax.css" | prepend: site.baseurl | prepend: site.url}}">
  <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}">
  <link rel="shortcut icon" type ="image/x-icon" href="{{ site.url }}{{ site.baseurl }}/images/favicon.ico">
  <link href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap-glyphicons.css" rel="stylesheet">
  <link rel="stylesheet" href="/css/common.css">

  {% if layout.custom_css %}
  {% for stylesheet in layout.custom_css %}
  <link rel="stylesheet" href="/css/{{ stylesheet }}.css">
  {% endfor %}
  {% endif %}
  {% if page.custom_css %}
  {% for stylesheet in page.custom_css %}
  <link rel="stylesheet" href="/css/{{ stylesheet }}.css">
  {% endfor %}
  {% endif %}

  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>

  {% if layout.custom_js %}
  {% for javascript in layout.custom_js %}
  <script src="/js/{{ javascript }}.js" />
  {% endfor %}
  {% endif %}
  {% if page.custom_js %}
  {% for javascript in page.custom_js %}
  <script src="/js/{{ javascript }}.js" />
  {% endfor %}
  {% endif %}

  <!-- Mathjax Support -->
  <script type="text/javascript" async
          src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML">
  </script>

  {% if jekyll.environment == 'production' %}
  {% include analytics.html %}
  {% endif %}
</head>