The empty boxes are supposed to be filled with ads, but are not working consistently yet. This new way of rendering ads is supposed to be reduce the amount of jumping around on the screen, but it doesn’t work for the “Light” theme, only the regular CC theme. You will need to switch back to the regular theme to see those boxes filled.
The Light theme will likely be going away soon as we transition our ads to a new provider.
More to come soon as we solidify our plans!