Confirm that the customizer blocks IE<=9, or fix it so that it does.
Created by: cvrebert
Refs https://github.com/twbs/bootstrap/pull/12773#issuecomment-37786214 & #12617 (closed).
Created by: cvrebert
Refs https://github.com/twbs/bootstrap/pull/12773#issuecomment-37786214 & #12617 (closed).