:last-child

I'm trying to create a horizontal nav bar with "::" as a separator. I want to use :last child so that the last item does not have the separator after it.
The problem is that as soon as I put the :last-child code in, it overrides the styling for the whole list.

I tried using :after first - but had the same issue, so I decided to try the less-elegant solution of a background image.

Then I tried a transparent image "space.png." Blue dots still disappear with :last-child. For testing I made "space.png" into pink dots.