intro grammar fixes :)

index.html

@@ -48,12 +48,12 @@
     
     So you'd like to know how to use impress.js?
     
-    You've made the first, very important step - you're reading the source code.
-    And that's how impress.js presentations are built - with HTML and CSS code.
+    You've made the first, very important step: you're reading the source code.
+    And that's how impress.js presentations are built-- with HTML and CSS code.
     
     Believe me, you need quite decent HTML and CSS skills to be able to use impress.js effectively.
-    And what is even more important, you need to be a designer, too, because there are no default
-    styles for impress.js presentations, there is no default or automatic layout for them.
+    And what is even more important is that you need to be a designer too, because there are no default
+    styles for impress.js presentations and there is no default or automatic layout for them.
     
     You need to design and build it by hand.
     
@@ -198,7 +198,7 @@
         Again, we use a `data-` attribute, this time it's `data-scale="4"`, so it means that this
         element will be 4 times larger than the others.
         From presentation and transitions point of view it means, that it will have to be scaled
-        down (4 times) to make it back to it's correct size.
+        down (4 times) to make it back to its correct size.
         
     -->
     <div id="title" class="step" data-x="0" data-y="0" data-scale="4">