diff --git a/README.md b/README.md
index 83db1759..b62f77ab 100644
--- a/README.md
+++ b/README.md
@@ -565,7 +565,7 @@ Put the compiled JS files into HTML.
 - [React (Virtual) DOM Terminology](http://facebook.github.io/react/docs/glossary.html), by Sebastian Markbåge
 - [The React Quick Start Guide](http://www.jackcallister.com/2015/01/05/the-react-quick-start-guide.html), by Jack Callister
 - [Learning React.js: Getting Started and Concepts](https://scotch.io/tutorials/learning-react-getting-started-and-concepts), by Ken Wheeler
-- [Getting started with React](http://ryanclark.me/getting-started-with-react/), by Ryan Clark
+- [Getting started with React](http://ryanclark.me/getting-started-with-react), by Ryan Clark
 - [React JS Tutorial and Guide to the Gotchas](https://zapier.com/engineering/react-js-tutorial-guide-gotchas/), by Justin Deal
 - [React Primer](https://github.com/BinaryMuse/react-primer), by Binary Muse
 - [jQuery versus React.js thinking](http://blog.zigomir.com/react.js/jquery/2015/01/11/jquery-versus-react-thinking.html), by zigomir
diff --git a/demo02/index.html b/demo02/index.html
index c0690997..48c6c9ec 100644
--- a/demo02/index.html
+++ b/demo02/index.html
@@ -13,8 +13,8 @@
       ReactDOM.render(
         <div>
         {
-          names.map(function (name) {
-            return <div>Hello, {name}!</div>
+          names.map(function (name, index) {
+            return <div key={index}>Hello, {name}!</div>
           })
         }
         </div>,
diff --git a/demo03/index.html b/demo03/index.html
index 4898c4f4..7c0645b8 100644
--- a/demo03/index.html
+++ b/demo03/index.html
@@ -9,8 +9,8 @@
     <div id="example"></div>
     <script type="text/babel">
       var arr = [
-        <h1>Hello world!</h1>,
-        <h2>React is awesome</h2>,
+        <h1 key="1">Hello world!</h1>,
+        <h2 key="2">React is awesome</h2>,
       ];
       ReactDOM.render(
         <div>{arr}</div>,