Drop the right and left margins on box to 10px.

This should fix [bug 932675 on bugzilla](https://bugzilla.mozilla.org/show_bug.cgi?id=932675).

I'm quite new to contributing code to mozilla so feel free to point me in the right direction if I'm doing something wrong.

For example I'm not sure if there is a design we can't deviate from or anything since this will solve the problem in a way that is visibly different.