Comment to help user understand 'mountNode' on home page example.

content/home/examples/a-component-using-external-plugins.js

@@ -36,4 +36,7 @@ class MarkdownEditor extends React.Component {
   }
 }
 
-ReactDOM.render(<MarkdownEditor />, mountNode);
+ReactDOM.render(
+  <MarkdownEditor />,
+  document.getElementById('external-plugin-example')
+);

content/home/examples/a-simple-component.js

@@ -8,7 +8,8 @@ class HelloMessage extends React.Component {
   }
 }
 
+
 ReactDOM.render(
   <HelloMessage name="Taylor" />,
-  mountNode
-);
+  document.getElementById('simple-component')
+);

content/home/examples/a-stateful-component.js

@@ -27,4 +27,7 @@ class Timer extends React.Component {
   }
 }
 
-ReactDOM.render(<Timer />, mountNode);
+ReactDOM.render(
+  <Timer />,
+  document.getElementById('stateful-component')
+);

content/home/examples/an-application.js

@@ -60,4 +60,7 @@ class TodoList extends React.Component {
   }
 }
 
-ReactDOM.render(<TodoApp />, mountNode);
+ReactDOM.render(
+  <TodoApp />,
+  document.getElementById('application')
+);