can you just use the `.light-bg` css on the body to do these anyway? e.g. `.light-bg footer { display: none; }`

i'm wary of sticking all this display logic in the js because then we have two places to go to change the way the site looks.

also, while we're at it can we choose a better name than "light-bg" for this? it's a modal backdrop essentially right? just a thoguht, I don't have a better name off-hand.