add note for exercise 16 to avoid common confusion

index.html

@@ -50,12 +50,12 @@
 	</div>
 	<h1 class="center">Functional Programming in Javascript</h1>
 
-	<p>This is a series of interactive exercises for learning Microsoft's Reactive Extensions (Rx) Library for Javascript. 
-		So why is the title "Functional Programming in Javascript"? Well it turns out that the key to learning Rx is 
-		training yourself to use functional programming to manipulate collections.  Functional programming provides 
-		developers with the tools to abstract common collection operations into reusable, composable building blocks. 
+	<p>This is a series of interactive exercises for learning Microsoft's Reactive Extensions (Rx) Library for Javascript.
+		So why is the title "Functional Programming in Javascript"? Well it turns out that the key to learning Rx is
+		training yourself to use functional programming to manipulate collections.  Functional programming provides
+		developers with the tools to abstract common collection operations into reusable, composable building blocks.
 		You'll be surprised to learn that most of the operations you perform on collections can be accomplished with
-		<b>five simple functions</b> (some native to JavaScript and some included in the 
+		<b>five simple functions</b> (some native to JavaScript and some included in the
 		<a href="https://github.com/Reactive-Extensions/RxJS">RxJS library</a>):
 	</p>
 	<ol>
@@ -1877,7 +1877,7 @@ <h4>Exercise 15: Use forEach to find the largest box art</h4>
 	<div class="lesson">
 		<h4>Exercise 16: Implement reduce()</h4>
 
-		<p>Let's add a reduce() function to the Array type. Like map</p>
+		<p>Let's add a reduce() function to the Array type. Like map. Take note this is <b>different from the reduce in ES5</b>, which returns an value instead of an Array! </p>
 		<textarea class="code" rows="40" cols="80">
 			// [1,2,3].reduce(function(accumulatedValue, currentValue) { return accumulatedValue + currentValue; }); === [6];
 			// [1,2,3].reduce(function(accumulatedValue, currentValue) { return accumulatedValue + currentValue; }, 10); === [16];