diff --git a/conf/default.conf.php b/conf/default.conf.php
index 8a3003eb43..62ce6b2b35 100644
--- a/conf/default.conf.php
+++ b/conf/default.conf.php
@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -427,6 +427,10 @@ return array(
   // You can enable traces for development to make it easier to debug problems.
   'phabricator.show-stack-traces' => false,
 
+  // Shows an error callout if a page generated PHP errors, warnings or notices.
+  // This makes it harder to miss problems while developing Phabricator.
+  'phabricator.show-error-callout' => false,
+
   // When users write comments which have URIs, they'll be automaticaly linked
   // if the protocol appears in this set. This whitelist is primarily to prevent
   // security issues like javascript:// URIs.
diff --git a/conf/development.conf.php b/conf/development.conf.php
index 34edf822a1..963e6a88b2 100644
--- a/conf/development.conf.php
+++ b/conf/development.conf.php
@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,9 @@
 
 return array(
 
-  'darkconsole.enabled'           => true,
-  'celerity.force-disk-reads'     => true,
-  'phabricator.show-stack-traces' => true,
+  'darkconsole.enabled'             => true,
+  'celerity.force-disk-reads'       => true,
+  'phabricator.show-stack-traces'   => true,
+  'phabricator.show-error-callout'  => true,
 
 ) + phabricator_read_config_file('default');
diff --git a/src/view/page/standard/PhabricatorStandardPageView.php b/src/view/page/standard/PhabricatorStandardPageView.php
index a68baf7d92..b8859dbf28 100644
--- a/src/view/page/standard/PhabricatorStandardPageView.php
+++ b/src/view/page/standard/PhabricatorStandardPageView.php
@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -364,8 +364,19 @@ class PhabricatorStandardPageView extends AphrontPageView {
         '</div>';
     }
 
+    $developer_warning = null;
+    if (PhabricatorEnv::getEnvConfig('phabricator.show-error-callout') &&
+        DarkConsoleErrorLogPluginAPI::getErrors()) {
+      $developer_warning =
+        '<div class="aphront-developer-error-callout">'.
+          'This page raised PHP errors. Find them in DarkConsole '.
+          'or the error log.'.
+        '</div>';
+    }
+
     return
       ($console ? '<darkconsole />' : null).
+      $developer_warning.
       '<div class="phabricator-standard-page '.$admin_class.'">'.
         $header_chrome.
         $this->bodyContent.
diff --git a/src/view/page/standard/__init__.php b/src/view/page/standard/__init__.php
index 6acc29d440..f07d67355c 100644
--- a/src/view/page/standard/__init__.php
+++ b/src/view/page/standard/__init__.php
@@ -6,6 +6,7 @@
 
 
 
+phutil_require_module('phabricator', 'aphront/console/plugin/errorlog/api');
 phutil_require_module('phabricator', 'aphront/request');
 phutil_require_module('phabricator', 'applications/people/storage/preferences');
 phutil_require_module('phabricator', 'infrastructure/celerity/api');
diff --git a/webroot/rsrc/css/application/base/standard-page-view.css b/webroot/rsrc/css/application/base/standard-page-view.css
index 6f117d88dd..fc2235fa10 100644
--- a/webroot/rsrc/css/application/base/standard-page-view.css
+++ b/webroot/rsrc/css/application/base/standard-page-view.css
@@ -179,3 +179,12 @@ td.phabricator-login-details {
   font-family:        "Menlo", "Consolas", "Monaco", monospace;
   font-size:          10px;
 }
+
+.aphront-developer-error-callout {
+  padding: 2em;
+  background: #aa0000;
+  color: white;
+  text-align: center;
+  font-size: 11px;
+  font-family: "Verdana";
+}