_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">

  {% if site.plugins contains 'jekyll-seo-tag' or site.gems contains 'jekyll-seo-tag' %}
    {% comment %}
      Add metadata for search engines and social networks if jekyll-seo-tag plugin is enabled
    {% endcomment %}
    {% include head-seo.html %}
  {% else %}
    <title>{% if page.title %}{{ page.title | escape }}{% else %}{{ site.title | escape }}{% endif %}</title>
    <meta name="description" content="{{ page.excerpt | default: site.description | strip_html | normalize_whitespace | truncate: 160 | escape }}">
    <link rel="canonical" href="{{ page.url | replace:'index.html', '' | absolute_url }}">
  {% endif %}

  <script>
    /* Cut the mustard */
    if ( 'querySelector' in document && 'addEventListener' in window ) {
      document.documentElement.className = document.documentElement.className.replace(/\bno-js\b/g, '') + 'js';
    }
  </script>

  <link rel="stylesheet" href="{{ '/assets/stylesheets/main.css' | relative_url }}">
  {% if site.data.theme.google_fonts %}
    <link rel="stylesheet" href="https://fonts.googleapis.com/css?family={% for font in site.data.theme.google_fonts %}{{ font.name | replace: ' ', '+' }}{% if font.weights %}:{% endif %}{{ font.weights | remove: ' ' }}{% if forloop.last != true %}|{% endif %}{% endfor %}">
  {% endif %}

  {% if site.plugins contains 'jekyll-feed' or site.gems contains 'jekyll-feed'%}
    {% comment %}
      Add Atom feed link if jekyll-feed plugin is enabled
    {% endcomment %}
    {% include head-feed.html %}
  {% endif %}
</head>