Minor changes to Introduction section (#432)

index.html

@@ -185,7 +185,7 @@ <h2>
       <p>
         Devices with limited screen size lack the ability to show Web content
         to a larger audience: a group of colleagues in a conference room, or
-        friends and family at home. Web content shown on a larger
+        friends and family at home, for example. Web content shown on a larger
         <a>presentation display</a> has greater perceived quality, legibility,
         and impact.
       </p>
@@ -223,7 +223,7 @@ <h2>
         mode</dfn> implementation of the Presentation API.
       </p>
       <p>
-        The Presentation API defined is intended to be used with user agents
+        The Presentation API is intended to be used with user agents
         that attach to <a>presentation displays</a> in <a>1-UA mode</a>,
         <a>2-UA mode</a>, and possibly other means not listed above. To improve
         interoperability between user agents and presentation displays,