IE9’s compatibility code is one of the most annoying things in my opinion. For some reason it’s the default even when the site looks fine with it off….. and it can make the website look crap when it’s on.

To get rid of it (or switch it off by default I’m not sure) just add this to the header along with the other meta data

<meta http-equiv="X-UA-Compatible" content="IE=Edge" />