Removed floating from .imageholder in mobile media query to fix positioning & sizing bug on certain mobile devices.

Certain mobile phones (for example Nokia Lumias) have an issue with the float: right in imageholder and display images like this then:
http://i.imgur.com/DkcIQUk.jpg

So I removed the float: right from .imageholder and also added a closing bracket for the mobile media query, and this is what it looks like now:
http://i.imgur.com/aGP7Lpb.jpg