diff --git a/_config.yml b/_config.yml
index 10c213f..734598f 100644
--- a/_config.yml
+++ b/_config.yml
@@ -7,8 +7,9 @@ theme: jekyll-theme-chirpy
 # change below value to '/projectname'.
 baseurl: ''
 
-# The language of the site layout › http://www.lingoes.net/en/translator/langcode.htm
-# Go to folder '_data/locales' to check the available language options
+# The language of the webpage › http://www.lingoes.net/en/translator/langcode.htm
+# If it has the same name as one of the files in folder `_data/locales`, the layout language will also be changed,
+# otherwise, the layout language will use the default value of 'en'.
 lang: en
 
 # Change to your timezone › http://www.timezoneconverter.com/cgi-bin/findzone/findzone
diff --git a/_includes/footer.html b/_includes/footer.html
index d84c8bb..582cb4c 100644
--- a/_includes/footer.html
+++ b/_includes/footer.html
@@ -8,9 +8,9 @@
       <p class="mb-0">
         © {{ 'now' | date: "%Y" }}
         <a href="{{ site.social.links[0] }}">{{ site.social.name }}</a>.
-        {% if site.data.locales[site.lang].copyright.brief %}
+        {% if site.data.locales[lang].copyright.brief %}
         <span data-toggle="tooltip" data-placement="top"
-          title="{{ site.data.locales[site.lang].copyright.verbose }}">{{ site.data.locales[site.lang].copyright.brief }}</span>
+          title="{{ site.data.locales[lang].copyright.verbose }}">{{ site.data.locales[lang].copyright.brief }}</span>
         {% endif %}
       </p>
     </div>
@@ -25,7 +25,7 @@
           <a href="https://github.com/cotes2020/jekyll-theme-chirpy" target="_blank" rel="noopener">Chirpy</a>
         {% endcapture %}
 
-        {{ site.data.locales[site.lang].meta
+        {{ site.data.locales[lang].meta
           | default: 'Powered by :PLATFORM with :THEME theme.'
           | replace: ':PLATFORM', _platform | replace: ':THEME', _theme
         }}
diff --git a/_includes/head.html b/_includes/head.html
index 47e616d..710d47d 100644
--- a/_includes/head.html
+++ b/_includes/head.html
@@ -8,11 +8,11 @@
 
   {% if page.layout == 'home' or page.layout == 'post' %}
 
-    <!-- i18n for timeago.js -->
-    <meta name="day-prompt" content="{{ site.data.locales[site.lang].post.timeago.day | default: "d ago" }}">
-    <meta name="hour-prompt" content="{{ site.data.locales[site.lang].post.timeago.hour | default: "hr ago" }}">
-    <meta name="minute-prompt" content="{{ site.data.locales[site.lang].post.timeago.minute | default: "min ago" }}">
-    <meta name="justnow-prompt" content="{{ site.data.locales[site.lang].post.timeago.just_now | default: "just now" }}">
+    <!-- i18n for `_javascript/utils/timeago.js` -->
+    <meta name="day-prompt" content="{{ site.data.locales[lang].post.timeago.day }}">
+    <meta name="hour-prompt" content="{{ site.data.locales[lang].post.timeago.hour }}">
+    <meta name="minute-prompt" content="{{ site.data.locales[lang].post.timeago.minute }}">
+    <meta name="justnow-prompt" content="{{ site.data.locales[lang].post.timeago.just_now }}">
 
     {% if site.google_analytics.pv.proxy_endpoint %}
       <meta name="pv-proxy-endpoint" content="{{ site.google_analytics.pv.proxy_endpoint }}">
diff --git a/_includes/lang.html b/_includes/lang.html
new file mode 100644
index 0000000..656f200
--- /dev/null
+++ b/_includes/lang.html
@@ -0,0 +1,8 @@
+{% comment %}
+Detect appearance language and return it through variable "lang"
+{% endcomment %}
+{% if site.data.locales[site.lang] %}
+  {% assign lang = site.lang %}
+{% else %}
+  {% assign lang = 'en' %}
+{% endif %}
diff --git a/_includes/panel.html b/_includes/panel.html
index bfa881b..98b859c 100644
--- a/_includes/panel.html
+++ b/_includes/panel.html
@@ -2,6 +2,8 @@
   The Pannel on right side (Desktop views)
 -->
 
+{% include lang.html %}
+
 <div id="panel-wrapper" class="col-xl-3 pl-2 text-muted topbar-down">
 
   <div class="access">
@@ -11,7 +13,7 @@
   {% if update_list.size > 0 %}
 
     <div id="access-lastmod" class="post">
-      <span>{{- site.data.locales[site.lang].panel.lastmod | default: 'Recent Update' -}}</span>
+      <span>{{- site.data.locales[lang].panel.lastmod -}}</span>
       <ul class="post-content pl-0 pb-1 ml-1 mt-2">
 
       {% for item in update_list %}
@@ -30,7 +32,7 @@
 
   {% if trending_tags.size > 0 %}
     <div id="access-tags">
-      <span>{{- site.data.locales[site.lang].panel.trending_tags | default: 'Trending Tags' -}}</span>
+      <span>{{- site.data.locales[lang].panel.trending_tags -}}</span>
       <div class="d-flex flex-wrap mt-3 mb-1 mr-3">
 
       {% for tag_name in trending_tags %}
@@ -48,7 +50,7 @@
     <script src="https://cdn.jsdelivr.net/gh/afeld/bootstrap-toc@1.0.1/dist/bootstrap-toc.min.js"></script>
     <div id="toc-wrapper" class="pl-0 pr-4 mb-5">
       <span class="pl-3 pt-2 mb-2">
-      {{- site.data.locales[site.lang].panel.toc | default: 'Contents' -}}
+      {{- site.data.locales[lang].panel.toc -}}
       </span>
       <nav id="toc" data-toggle="toc"></nav>
     </div>
diff --git a/_includes/post-nav.html b/_includes/post-nav.html
index c9c258c..bb3b52d 100644
--- a/_includes/post-nav.html
+++ b/_includes/post-nav.html
@@ -5,24 +5,24 @@
 <div class="post-navigation d-flex justify-content-between">
   {% if page.previous.url %}
   <a href="{{ site.baseurl }}{{ page.previous.url }}" class="btn btn-outline-primary"
-    prompt="{{ site.data.locales[site.lang].post.button.previous | default: 'previous' }}">
+    prompt="{{ site.data.locales[lang].post.button.previous }}">
     <p>{{ page.previous.title }}</p>
   </a>
   {% else %}
   <span class="btn btn-outline-primary disabled"
-    prompt="{{ site.data.locales[site.lang].post.button.previous | default: 'previous' }}">
+    prompt="{{ site.data.locales[lang].post.button.previous }}">
     <p>-</p>
   </span>
   {% endif %}
 
   {% if page.next.url %}
   <a href="{{ site.baseurl }}{{page.next.url}}" class="btn btn-outline-primary"
-    prompt="{{ site.data.locales[site.lang].post.button.next | default: 'next' }}">
+    prompt="{{ site.data.locales[lang].post.button.next }}">
     <p>{{ page.next.title }}</p>
   </a>
   {% else %}
   <span class="btn btn-outline-primary disabled"
-    prompt="{{ site.data.locales[site.lang].post.button.next | default: 'next' }}">
+    prompt="{{ site.data.locales[lang].post.button.next }}">
     <p>-</p>
   </span>
   {% endif %}
diff --git a/_includes/post-sharing.html b/_includes/post-sharing.html
index 252370f..4bf7d8d 100644
--- a/_includes/post-sharing.html
+++ b/_includes/post-sharing.html
@@ -3,7 +3,7 @@
 -->
 
 <div class="share-wrapper">
-  <span class="share-label text-muted mr-1">{{ site.data.locales[site.lang].post.share | default: 'Share' }}</span>
+  <span class="share-label text-muted mr-1">{{ site.data.locales[lang].post.share }}</span>
   <span class="share-icons">
     {% capture title %}{{ page.title }} - {{ site.title }}{% endcapture %}
     {% assign url = page.url | absolute_url %}
@@ -16,9 +16,9 @@
         </a>
     {% endfor %}
 
-    <i class="fa-fw fas fa-link small" onclick="copyLink('', '{{ site.data.locales[site.lang].post.button.copy.succeed }}')"
+    <i class="fa-fw fas fa-link small" onclick="copyLink('', '{{ site.data.locales[lang].post.button.copy.succeed }}')"
         data-toggle="tooltip" data-placement="top"
-        title="{{ site.data.locales[site.lang].post.button.copy.title }}">
+        title="{{ site.data.locales[lang].post.button.copy.title }}">
     </i>
 
   </span>
diff --git a/_includes/read-time.html b/_includes/read-time.html
index 460c65a..e537693 100644
--- a/_includes/read-time.html
+++ b/_includes/read-time.html
@@ -16,13 +16,13 @@
 {% endunless %}
 
 {% capture read_prompt %}
-  {{- site.data.locales[site.lang].post.read_time.prompt | default: "read" -}}
+  {{- site.data.locales[lang].post.read_time.prompt -}}
 {% endcapture %}
 
 <!-- return element -->
 <span class="readtime" data-toggle="tooltip" data-placement="bottom"
-  title="{{ words }} {{ site.data.locales[site.lang].post.words | default: "words" }}">
-  {{- read_time -}}{{" "}}{{- site.data.locales[site.lang].post.read_time.unit | default: "min" -}}
+  title="{{ words }} {{ site.data.locales[lang].post.words }}">
+  {{- read_time -}}{{" "}}{{- site.data.locales[lang].post.read_time.unit -}}
   {%- if include.prompt -%}
     {% unless site.lang contains 'zh' %}{{" "}}{% endunless %}{{ read_prompt }}
   {%- endif -%}
diff --git a/_includes/related-posts.html b/_includes/related-posts.html
index d4c3996..910de53 100644
--- a/_includes/related-posts.html
+++ b/_includes/related-posts.html
@@ -81,7 +81,7 @@
 {% if index_list.size > 0 %}
   <div id="related-posts" class="mt-5 mb-2 mb-sm-4">
     <h3 class="pt-2 mt-1 mb-4 ml-1"
-      data-toc-skip>{{ site.data.locales[site.lang].post.relate_posts | default: 'Further Reading' }}</h3>
+      data-toc-skip>{{ site.data.locales[lang].post.relate_posts }}</h3>
     <div class="card-deck mb-4">
     {% for entry in index_list %}
       {% assign index = entry | plus: 0 %}
diff --git a/_includes/search-results.html b/_includes/search-results.html
index 07e180a..166ed5f 100644
--- a/_includes/search-results.html
+++ b/_includes/search-results.html
@@ -4,7 +4,7 @@
 <div id="search-result-wrapper" class="d-flex justify-content-center unloaded">
   <div class="col-12 col-sm-11 post-content">
     <div id="search-hints">
-      <h4 class="text-muted mb-4">{{ site.data.locales[site.lang].panel.trending_tags | default: 'Trending Tags' }}</h4>
+      <h4 class="text-muted mb-4">{{ site.data.locales[lang].panel.trending_tags }}</h4>
 
       {% include trending-tags.html %}
 
diff --git a/_includes/sidebar.html b/_includes/sidebar.html
index 8497fa4..b32d717 100644
--- a/_includes/sidebar.html
+++ b/_includes/sidebar.html
@@ -32,7 +32,7 @@
     <li class="nav-item{% if page.layout == 'home' %}{{ " active" }}{% endif %}">
       <a href="{{ '/' | relative_url }}" class="nav-link">
         <i class="fa-fw fas fa-home ml-xl-3 mr-xl-3 unloaded"></i>
-        <span>{{ site.data.locales[site.lang].tabs.home | default: "home" | upcase }}</span>
+        <span>{{ site.data.locales[lang].tabs.home | upcase }}</span>
       </a>
     </li>
     <!-- the real tabs -->
@@ -42,7 +42,7 @@
         <i class="fa-fw {{ tab.icon }} ml-xl-3 mr-xl-3 unloaded"></i>
         {% capture tab_name %}{{ tab.url | split: '/' }}{% endcapture %}
 
-        <span>{{ site.data.locales[site.lang].tabs.[tab_name] | default: tab_name | upcase }}</span>
+        <span>{{ site.data.locales[lang].tabs.[tab_name] | default: tab_name | upcase }}</span>
       </a>
     </li> <!-- .nav-item -->
     {% endfor %}
diff --git a/_includes/timeago.html b/_includes/timeago.html
index 91e42ec..b68e08b 100644
--- a/_includes/timeago.html
+++ b/_includes/timeago.html
@@ -3,9 +3,9 @@
   See: /assets/js/_utils/timeage.js
 -->
 
-{% assign tooltip_df = site.data.locales[site.lang].date_format.tooltip | default: '%a, %b %e, %Y, %l:%M %p %z' %}
-{% assign post_long_df = site.data.locales[site.lang].date_format.post.long | default: '%b %e, %Y' %}
-{% assign post_short_df = site.data.locales[site.lang].date_format.post.short | default: '%b %e' %}
+{% assign tooltip_df = site.data.locales[lang].date_format.tooltip %}
+{% assign post_long_df = site.data.locales[lang].date_format.post.long %}
+{% assign post_short_df = site.data.locales[lang].date_format.post.short %}
 
 {% if include.preposition %}
   {{ include.preposition }}
diff --git a/_includes/topbar.html b/_includes/topbar.html
index c8eed87..6ecc176 100644
--- a/_includes/topbar.html
+++ b/_includes/topbar.html
@@ -10,7 +10,7 @@
 
     {% if paths.size == 0 or page.layout == 'home' %}
       <!-- index page -->
-      <span>{{ site.data.locales[site.lang].tabs.home | default: 'home' | capitalize }}</span>
+      <span>{{ site.data.locales[lang].tabs.home | capitalize }}</span>
 
     {% else %}
 
@@ -19,14 +19,14 @@
         {% if forloop.first %}
           <span>
             <a href="{{ '/' | relative_url }}">
-              {{ site.data.locales[site.lang].tabs.home | default: 'home' | capitalize }}
+              {{ site.data.locales[lang].tabs.home | capitalize }}
             </a>
           </span>
 
         {% elsif forloop.last %}
 
           {% if page.collection == 'tabs' %}
-            <span>{{ site.data.locales[site.lang].tabs[item] | default: page.title }}</span>
+            <span>{{ site.data.locales[lang].tabs[item] | default: page.title }}</span>
           {% else %}
             <span>{{ page.title }}</span>
           {% endif %}
@@ -36,7 +36,7 @@
           {% unless page.layout == 'post' %}
             <span>
               <a href="{{ item | relative_url }}">
-                {{ site.data.locales[site.lang].tabs[item] | default: page.title }}
+                {{ site.data.locales[lang].tabs[item] | default: page.title }}
               </a>
             </span>
           {% endunless %}
@@ -53,12 +53,12 @@
 
     <div id="topbar-title">
       {% if page.layout == 'home' %}
-        {{- site.data.locales[site.lang].title | default: site.title -}}
+        {{- site.data.locales[lang].title | default: site.title -}}
       {% elsif page.collection == 'tabs' %}
         {%- capture tab_key -%}{{ page.url | split: '/' }}{%- endcapture -%}
-        {{- site.data.locales[site.lang].tabs[tab_key] | default: page.title -}}
+        {{- site.data.locales[lang].tabs[tab_key] | default: page.title -}}
       {% else %}
-        {{- site.data.locales[site.lang].layout[page.layout] | default: page.layout | capitalize -}}
+        {{- site.data.locales[lang].layout[page.layout] | default: page.layout | capitalize -}}
       {% endif %}
     </div>
 
@@ -66,10 +66,10 @@
     <span id="search-wrapper" class="align-items-center">
       <i class="fas fa-search fa-fw"></i>
       <input class="form-control" id="search-input" type="search"
-        aria-label="search" autocomplete="off" placeholder="{{ site.data.locales[site.lang].search.hint | default: 'Search' | capitalize }}...">
+        aria-label="search" autocomplete="off" placeholder="{{ site.data.locales[lang].search.hint | capitalize }}...">
       <i class="fa fa-times-circle fa-fw" id="search-cleaner"></i>
     </span>
-    <span id="search-cancel" >{{ site.data.locales[site.lang].search.cancel | default: 'Cancel' }}</span>
+    <span id="search-cancel" >{{ site.data.locales[lang].search.cancel }}</span>
   </div>
 
 </div>
diff --git a/_layouts/archives.html b/_layouts/archives.html
index 634958f..dfb2d32 100644
--- a/_layouts/archives.html
+++ b/_layouts/archives.html
@@ -3,6 +3,8 @@ layout: page
 # The Archives of posts.
 ---
 
+{% include lang.html %}
+
 <div id="archives" class="pl-xl-2">
 
 {% for post in site.posts %}
@@ -17,7 +19,7 @@ layout: page
     <li>
       <div>
         {% capture this_day %}{{ post.date | date: "%d" }}{% endcapture %}
-        {% capture _mth_df %}{{ site.data.locales[site.lang].date_format.post.archive_month | default: "%b" }}{% endcapture %}
+        {% capture _mth_df %}{{ site.data.locales[lang].date_format.post.archive_month }}{% endcapture %}
         {% capture this_month %}{{ post.date | date: _mth_df }}{% endcapture %}
         <span class="date day">{{ this_day }}</span>
         <span class="date month small text-muted">{% include no-zero-date.html date_str=this_month %}</span>
diff --git a/_layouts/categories.html b/_layouts/categories.html
index 669f48f..4e9ce77 100644
--- a/_layouts/categories.html
+++ b/_layouts/categories.html
@@ -3,6 +3,8 @@ layout: page
 # All the Categories of posts
 ---
 
+{% include lang.html %}
+
 {% assign HEAD_PREFIX = "h_" %}
 {% assign LIST_PREFIX = "l_" %}
 
@@ -45,10 +47,10 @@ layout: page
         <span class="text-muted small font-weight-light">
           {% if sub_categories_size > 0 %}
             {{ sub_categories_size }}
-            {{ site.data.locales[site.lang].categories.category_measure | default: 'categories' }},
+            {{ site.data.locales[lang].categories.category_measure }},
           {% endif %}
             {{ top_posts_size }}
-            {{ site.data.locales[site.lang].categories.post_measure | default: 'posts' }}
+            {{ site.data.locales[lang].categories.post_measure }}
         </span>
       </span>
 
@@ -81,7 +83,7 @@ layout: page
           {% assign posts_size = site.categories[sub_category] | size %}
           <span class="text-muted small font-weight-light">
             {{ posts_size }}
-            {{ site.data.locales[site.lang].categories.post_measure | default: 'posts' }}
+            {{ site.data.locales[lang].categories.post_measure }}
           </span>
         </li>
         {% endfor %}
diff --git a/_layouts/category.html b/_layouts/category.html
index 60b8cd6..a366081 100644
--- a/_layouts/category.html
+++ b/_layouts/category.html
@@ -3,6 +3,8 @@ layout: page
 # The Category layout
 ---
 
+{% include lang.html %}
+
 <div id="page-category">
   <h1 class="pl-lg-2">
     <i class="far fa-folder-open fa-fw text-muted"></i>
@@ -11,7 +13,7 @@ layout: page
   </h1>
 
   <ul class="post-content pl-0">
-    {% assign post_df = site.data.locales[site.lang].date_format.post.long | default: '%b %e, %Y' %}
+    {% assign post_df = site.data.locales[lang].date_format.post.long %}
 
     {% for post in page.posts %}
     <li class="d-flex justify-content-between pl-md-3 pr-md-3">
diff --git a/_layouts/default.html b/_layouts/default.html
index 258a27a..2fe00e9 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -5,13 +5,15 @@ layout: compress
 
 <!DOCTYPE html>
 
+{% include lang.html %}
+
 {% capture prefer_mode %}
   {% if site.theme_mode %}
     mode="{{ site.theme_mode }}"
   {% endif %}
 {% endcapture %}
 
-<html lang="{{ site.lang | default: 'en' }}" {{ prefer_mode }}>
+<html lang="{{ site.lang }}" {{ prefer_mode }}>
 
   {% include head.html %}
 
diff --git a/_layouts/home.html b/_layouts/home.html
index 39e38e9..6cf5e3c 100644
--- a/_layouts/home.html
+++ b/_layouts/home.html
@@ -3,6 +3,8 @@ layout: page
 # The Home page layout
 ---
 
+{% include lang.html %}
+
 {% assign pinned = site.posts | where: "pin", "true" %}
 {% assign default = site.posts | where_exp: "item", "item.pin != true" %}
 
@@ -78,7 +80,7 @@ layout: page
       {% if post.pin %}
       <div class="pin">
         <i class="fas fa-thumbtack fa-fw"></i>
-        <span>{{ site.data.locales[site.lang].post.pin_prompt | default: 'Pinned' }}</span>
+        <span>{{ site.data.locales[lang].post.pin_prompt }}</span>
       </div>
       {% endif %}
 
diff --git a/_layouts/page.html b/_layouts/page.html
index 67d80b0..7afb697 100644
--- a/_layouts/page.html
+++ b/_layouts/page.html
@@ -10,7 +10,7 @@ layout: default
       <h1 class="dynamic-title">
         {% if page.collection == 'tabs' %}
           {%- capture tab_key -%}{{ page.url | split: '/' }}{%- endcapture -%}
-          {{- site.data.locales[site.lang].tabs[tab_key] | default: page.title -}}
+          {{- site.data.locales[lang].tabs[tab_key] | default: page.title -}}
         {% else %}
           {{- page.title -}}
         {% endif %}
diff --git a/_layouts/post.html b/_layouts/post.html
index d8b06a4..961f0de 100644
--- a/_layouts/post.html
+++ b/_layouts/post.html
@@ -3,6 +3,8 @@ layout: default
 # The posts' layout
 ---
 
+{% include lang.html %}
+
 <div class="row">
 
   <div id="post-wrapper" class="col-12 col-lg-11 col-xl-8">
@@ -17,7 +19,7 @@ layout: default
           <span class="semi-bold">
             {{ page.author | default: site.social.name }}
           </span>
-          {% capture _preposition %}{{ site.data.locales[site.lang].post.published | default: 'on' }}{% endcapture %}
+          {% capture _preposition %}{{ site.data.locales[lang].post.published }}{% endcapture %}
           {% include timeago.html date=page.date tooltip=true preposition=_preposition %}
         </div>
 
@@ -25,7 +27,7 @@ layout: default
           <!-- lastmod -->
           {% if page.last_modified_at %}
           <span>
-            {{ site.data.locales[site.lang].post.updated | default: 'Updated' }}
+            {{ site.data.locales[lang].post.updated }}
             {% include timeago.html date=page.last_modified_at class="lastmod" tooltip=true %}
           </span>
           {% endif %}
@@ -38,7 +40,7 @@ layout: default
           <span id="pv" class="pageviews">
             <i class="fas fa-spinner fa-spin fa-fw"></i>
           </span>
-          {{ site.data.locales[site.lang].post.pageview_measure | default: "views" }}
+          {{ site.data.locales[lang].post.pageview_measure }}
           {% endif %}
 
         </div>
@@ -89,13 +91,13 @@ layout: default
         <div class="post-tail-bottom
           d-flex justify-content-between align-items-center mt-3 pt-5 pb-2">
           <div class="license-wrapper">
-          {% if site.data.locales[site.lang].copyright.license.template %}
+          {% if site.data.locales[lang].copyright.license.template %}
             {% capture _replacement %}
-            <a href="{{ site.data.locales[site.lang].copyright.license.link }}">
-              {{ site.data.locales[site.lang].copyright.license.name }}
+            <a href="{{ site.data.locales[lang].copyright.license.link }}">
+              {{ site.data.locales[lang].copyright.license.name }}
             </a>
             {% endcapture %}
-            {{ site.data.locales[site.lang].copyright.license.template | replace: ':LICENSE_NAME', _replacement }}
+            {{ site.data.locales[lang].copyright.license.template | replace: ':LICENSE_NAME', _replacement }}
           {% endif %}
           </div>
 
diff --git a/_layouts/tag.html b/_layouts/tag.html
index eb75aef..30371ef 100644
--- a/_layouts/tag.html
+++ b/_layouts/tag.html
@@ -3,6 +3,8 @@ layout: page
 # The layout for Tag page
 ---
 
+{% include lang.html %}
+
 <div id="page-tag">
   <h1 class="pl-lg-2">
     <i class="fa fa-tag fa-fw text-muted"></i>
@@ -10,7 +12,7 @@ layout: page
     <span class="lead text-muted pl-2">{{ page.posts | size }}</span>
   </h1>
   <ul class="post-content pl-0">
-    {% assign post_df = site.data.locales[site.lang].date_format.post.long | default: '%b %e, %Y' %}
+    {% assign post_df = site.data.locales[lang].date_format.post.long %}
 
     {% for post in page.posts %}
     <li class="d-flex justify-content-between pl-md-3 pr-md-3">
diff --git a/assets/404.html b/assets/404.html
index d297a69..dde158a 100644
--- a/assets/404.html
+++ b/assets/404.html
@@ -11,19 +11,21 @@ redirect_from:
 dynamic_title: true
 ---
 
+{% include lang.html %}
+
 <div class="lead">
 
   {%- capture _head_back -%}
-    <a href="{{ '/' | relative_url }}">{{ site.data.locales[site.lang].not_found.head_back }}</a>
+    <a href="{{ '/' | relative_url }}">{{ site.data.locales[lang].not_found.head_back }}</a>
   {%- endcapture -%}
 
   {%- capture _archives_page -%}
-    <a href="{{ 'archives' | relative_url }}">{{ site.data.locales[site.lang].not_found.archives_page }}</a>
+    <a href="{{ 'archives' | relative_url }}">{{ site.data.locales[lang].not_found.archives_page }}</a>
   {%- endcapture -%}
 
-  <p>{{site.data.locales[site.lang].not_found.statment }}</p>
+  <p>{{site.data.locales[lang].not_found.statment }}</p>
 
-  <p>{{ site.data.locales[site.lang].not_found.hint_template
+  <p>{{ site.data.locales[lang].not_found.hint_template
     | replace: ':HEAD_BAK', _head_back
     | replace: ':ARCHIVES_PAGE', _archives_page }}
   </p>
diff --git a/assets/feed.xml b/assets/feed.xml
index 7e2f4e7..b36f4af 100644
--- a/assets/feed.xml
+++ b/assets/feed.xml
@@ -15,7 +15,7 @@ permalink: /feed.xml
     <uri>{{ "/" | absolute_url }}</uri>
   </author>
   <link rel="self" type="application/atom+xml" href="{{ page.url | absolute_url }}"/>
-  <link rel="alternate" type="text/html" hreflang="{{ site.lang | default: 'en' }}"
+  <link rel="alternate" type="text/html" hreflang="{{ site.lang }}"
     href="{{ '/' | absolute_url }}"/>
   <generator uri="https://jekyllrb.com/" version="{{ jekyll.version }}">Jekyll</generator>
   <rights> © {{ 'now' | date: '%Y' }} {{ site.social.name }} </rights>