diff --git a/_config.yml b/_config.yml
index 6354c7a..10c213f 100644
--- a/_config.yml
+++ b/_config.yml
@@ -11,11 +11,6 @@ baseurl: ''
 # Go to folder '_data/locales' to check the available language options
 lang: en
 
-# The lang attribute of HTML › http://www.lingoes.net/en/translator/langcode.htm
-# We can specify a language different from the layout of the content.
-# If it is not assigned, the site will use the value of 'lang' instead.
-content_lang: ''
-
 # Change to your timezone › http://www.timezoneconverter.com/cgi-bin/findzone/findzone
 timezone: Asia/Shanghai
 
@@ -173,6 +168,3 @@ jekyll-archives:
   permalinks:
     tag: /tags/:name/
     category: /categories/:name/
-
-# Outdated configuration warning
-outdated: '-- Missing configuration options! --'
diff --git a/_includes/footer.html b/_includes/footer.html
index aa5ff90..d84c8bb 100644
--- a/_includes/footer.html
+++ b/_includes/footer.html
@@ -11,8 +11,6 @@
         {% if site.data.locales[site.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>
-        {% else %}
-        <span class="text-muted">{{ site.outdated }}</span>
         {% endif %}
       </p>
     </div>
diff --git a/_layouts/default.html b/_layouts/default.html
index 0a39a80..258a27a 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -11,7 +11,7 @@ layout: compress
   {% endif %}
 {% endcapture %}
 
-<html lang="{{ site.content_lang | default: site.lang }}" {{ prefer_mode }}>
+<html lang="{{ site.lang | default: 'en' }}" {{ prefer_mode }}>
 
   {% include head.html %}
 
diff --git a/_layouts/post.html b/_layouts/post.html
index 4f4cef4..d8b06a4 100644
--- a/_layouts/post.html
+++ b/_layouts/post.html
@@ -96,8 +96,6 @@ layout: default
             </a>
             {% endcapture %}
             {{ site.data.locales[site.lang].copyright.license.template | replace: ':LICENSE_NAME', _replacement }}
-          {% else %}
-            <span class="text-muted small">{{ site.outdated }}</span>
           {% endif %}
           </div>
 
diff --git a/assets/feed.xml b/assets/feed.xml
index 97d2463..7e2f4e7 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.content_lang | default: site.lang }}"
+  <link rel="alternate" type="text/html" hreflang="{{ site.lang | default: 'en' }}"
     href="{{ '/' | absolute_url }}"/>
   <generator uri="https://jekyllrb.com/" version="{{ jekyll.version }}">Jekyll</generator>
   <rights> © {{ 'now' | date: '%Y' }} {{ site.social.name }} </rights>
