customizations within the admin panel – will they get replaced upon update?

I am customizing the directory theme by putting css in the custom css areas that are provided in the theme administration areas.

I am also customizing the listing page by using the “enable custom display” section under the themes/page setup/listing area.

My question is where are these customized bits of code stored? are they in the database?

What happens when you come out with version 9.0 and I update? will those customizations stay or disappear?

Thanks