--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/templates/404.html	Sun Jun 19 00:04:48 2016 +0800
@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+
+{% block title %}{{ message }}{% end %}
+
+{% block content %}
+  <div class="uk-container uk-container-center uk-margin-large-top">
+    <h1>{{ code }}</h1>
+    <h3>{{ message }}</h3>
+    {% if debug_message %}
+      <pre>{{ debug_message }}</pre>
+    {% end %}
+  </div>
+{% end %}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/templates/500.html	Sun Jun 19 00:04:48 2016 +0800
@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+
+{% block title %}{{ message }}{% end %}
+
+{% block content %}
+  <div class="uk-container uk-container-center uk-margin-large-top">
+    <h1>{{ code }}</h1>
+    <h3>{{ message }}</h3>
+    {% if debug_message %}
+      <pre>{{ debug_message }}</pre>
+    {% end %}
+  </div>
+{% end %}

--- a/viewer.py	Sat Jun 18 22:45:43 2016 +0800
+++ b/viewer.py	Sun Jun 19 00:04:48 2016 +0800
@@ -3,6 +3,7 @@
 
 import logging
 import os
+import traceback
 
 from peewee import DoesNotExist
 from tornado.escape import json_decode
@@ -39,6 +40,21 @@
         if not database.is_closed():
             database.close()
 
+    def write_error(self, status_code, **kwargs):
+        data = {
+            'code': status_code,
+            'message': self._reason,
+            'debug_message': ''
+        }
+        if 'exc_info' in kwargs:
+            if self.settings.get('serve_traceback'):
+                fexc = traceback.format_exception(*kwargs['exc_info'])
+                data['debug_message'] = '\n'.join(fexc)
+        if status_code == 404:
+            self.render('404.html', **data)
+        else:
+            self.render('500.html', **data)
+
 
 class IndexHandler(BaseHandler):
     def get(self):