Typo fix

index.html

@@ -281,7 +281,7 @@ function linkify( selector ) {
 					<h2>Take a Moment</h2>
 					<p>
 						Press b or period on your keyboard to enter the 'paused' mode. This mode is helpful when you want to take disctracting slides off the screen 
-						during a presentaion.
+						during a presentation.
 					</p>
 				</section>