Warning message if browser is IE7 or older

If the users browser is less or equal than IE7, a red warning bar will be displayed on top of the screen. It includes a link on how to update your browser (http://www.browser-update.org/update.html).

It looks like this on IE7 (hhu theme):
![ie-message-top](https://f.cloud.github.com/assets/1485226/547690/edc9d100-c2ca-11e2-8e41-b55db917bb40.jpg)