diff --git a/docs/contributing/code-reviewing.md b/docs/contributing/code-reviewing.md
index 7fb5ca82f6..edda35de4c 100644
--- a/docs/contributing/code-reviewing.md
+++ b/docs/contributing/code-reviewing.md
@@ -187,7 +187,7 @@ the maintainer time and get the PR merged quicker.
 
 We also strongly recommend reviewers to go through the following resources.
 
-* [The Gentle Art of Patch Review](http://sarah.thesharps.us/2014/09/01/the-gentle-art-of-patch-review/)
+* [The Gentle Art of Patch Review](http://sage.thesharps.us/2014/09/01/the-gentle-art-of-patch-review/)
   article by Sarah Sharp
 * [Zulip & Good Code Review](https://www.harihareswara.net/sumana/2016/05/17/0)
   article by Sumana Harihareswara
diff --git a/docs/tutorials/reading-list.md b/docs/tutorials/reading-list.md
index 489a371790..57f6471e34 100644
--- a/docs/tutorials/reading-list.md
+++ b/docs/tutorials/reading-list.md
@@ -134,7 +134,7 @@ Some titles have been shortened for organizational purposes.
 
 *Course* - [React native and redux course][]  (*Not free!*)
 
-[React native and redux course]: https://www.udemy.com/the-complete-react-native-and-redux-course/
+[React native and redux course]: https://www.udemy.com/course/the-complete-react-native-and-redux-course/
 
 *Slides* - [TypeScript vs. CoffeeScript vs. ES6][]
 
diff --git a/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py b/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
index e6630f6f73..599f29af26 100644
--- a/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
+++ b/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
@@ -23,6 +23,10 @@ EXCLUDED_URLS = [
     'https://circleci.com/gh/zulip/zulip/tree/master',
     'https://circleci.com/gh/zulip/zulip/16617',
     'https://www.linkedin.com/company/zulip-project',
+    # Returns 403 errors to HEAD requests
+    'https://giphy.com',
+    'https://giphy.com/apps/giphycapture',
+    'https://www.udemy.com/course/the-complete-react-native-and-redux-course/',
 ]
 
 VNU_IGNORE = re.compile(r'|'.join([