How do I style WordPress metaboxes?

I'm using Ultimate Branding to fully re-style the WordPress admin panel. I'm using Firebug to locate the classes and then copying and pasting into the CSS section of Ultimate Branding. Everything is working as it should except when it comes to the WordPress metaboxes. They absolutely won't style. I'll style them in Firebug, but when I copy and paste and then save, the styles don't change. Apparently WordPress core is doing something funky here, and I can't figure it out.

Any ideas?