diff --git a/404.php b/404.php
index ef30b33..51f0483 100644
--- a/404.php
+++ b/404.php
@@ -1,6 +1,6 @@
 <?php get_template_part('templates/page', 'header'); ?>
 
-<div class="alert">
+<div class="alert alert-warning">
   <?php _e('Sorry, but the page you were trying to view does not exist.', 'roots'); ?>
 </div>
 
diff --git a/base.php b/base.php
index af0ce18..6e76154 100644
--- a/base.php
+++ b/base.php
@@ -1,7 +1,7 @@
 <?php get_template_part('templates/head'); ?>
 <body <?php body_class(); ?>>
 
-  <!--[if lt IE 7]><div class="alert"><?php _e('You are using an <strong>outdated</strong> browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.', 'roots'); ?></div><![endif]-->
+  <!--[if lt IE 7]><div class="alert alert-warning"><?php _e('You are using an <strong>outdated</strong> browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.', 'roots'); ?></div><![endif]-->
 
   <?php
     do_action('get_header');
diff --git a/index.php b/index.php
index 6fb01ee..db54b2d 100644
--- a/index.php
+++ b/index.php
@@ -1,7 +1,7 @@
 <?php get_template_part('templates/page', 'header'); ?>
 
 <?php if (!have_posts()) : ?>
-  <div class="alert">
+  <div class="alert alert-warning">
     <?php _e('Sorry, no results were found.', 'roots'); ?>
   </div>
   <?php get_search_form(); ?>
diff --git a/templates/comment.php b/templates/comment.php
index fd1e40b..8454e7c 100644
--- a/templates/comment.php
+++ b/templates/comment.php
@@ -5,7 +5,7 @@
   <?php edit_comment_link(__('(Edit)', 'roots'), '', ''); ?>
 
   <?php if ($comment->comment_approved == '0') : ?>
-    <div class="alert">
+    <div class="alert alert-info">
       <?php _e('Your comment is awaiting moderation.', 'roots'); ?>
     </div>
   <?php endif; ?>
diff --git a/templates/comments.php b/templates/comments.php
index 3420103..1a93450 100644
--- a/templates/comments.php
+++ b/templates/comments.php
@@ -25,7 +25,7 @@
     <?php endif; ?>
 
     <?php if (!comments_open() && !is_page() && post_type_supports(get_post_type(), 'comments')) : ?>
-    <div class="alert">
+    <div class="alert alert-warning">
       <?php _e('Comments are closed.', 'roots'); ?>
     </div>
     <?php endif; ?>
@@ -34,7 +34,7 @@
 
 <?php if (!have_comments() && !comments_open() && !is_page() && post_type_supports(get_post_type(), 'comments')) : ?>
   <section id="comments">
-    <div class="alert">
+    <div class="alert alert-warning">
       <?php _e('Comments are closed.', 'roots'); ?>
     </div>
   </section><!-- /#comments -->
