I've got a real PITA problem to solve. Basically we design a web app in which we allow customers to import their CSS & HTML headers / footers and our content sits in the middle
natually this will mess up our CSS because of the cascading issue.
I can lock down specific components well enough but generic stuff such as font sizes cause problems
only way I can think to fix it is to use PX sizing for our font because ems / rems are reliant on the base font