It depends on what you want. The bootstrap container elements are 100% of the width but if you place things inside of them the have a small amount of padding.

Do have something specific you'd like to accomplish?

I'm trying to put a navigation bar inside a fluid container (like any static navigation headers), it doesn't seem to work :<

Ah. Navigation bars are intended to go outside of containers. You can make it span the entire width by setting the position in the inspector to "fixed top".