Fix some small typos on the about page

public/templates/about.html

@@ -26,7 +26,7 @@ <h2>No registration, no cost and no ads</h2>
 <p>Unlike other, similiar services out there, tempalias doesn't require you to
 create an account or provide any personal information (other than your
 real email address, of course). Also, the service is completely cost and
-advertisment free.</p>
+advertisement free.</p>
 
 <h2>Background and tech stuff</h2>
 <p>tempalias is a grown-up proof of concept showing that it is possible
@@ -41,13 +41,13 @@ <h2>Background and tech stuff</h2>
 <a href="http://www.richardhaydon.com/">his services</a>.</p>
 
 <p>If you want to see how tempalias is done or if you want to run a
-comparable service yourself, the tempalias.com codebase is avilable
+comparable service yourself, the tempalias.com codebase is available
 licensed under the MIT license at
 <a href="http://github.com/pilif/tempalias">http://github.com/pilif/tempalias</a></p>
 
 <p>If you want to learn how Philip went from "no idea about asynchronous
 programming with node" to "completed tempalias.com", have a look at a
 series of blogposts about the topic. The best way to start would be to have a
-look at the official announcment:
+look at the official announcement:
 <a href="http://www.gnegg.ch/2010/04/announcing-tempalias-com/">http://www.gnegg.ch/2010/04/announcing-tempalias-com/</a>
 </p>