@
boogiepop oh.
you're using the live site.
beta reader makes more sense.
http://beta.mangadex.org/chapter/412424/1
if you have a landscape orientated monitor, fit to height and fit to container will pretty much always do the same thing (except for super wide images like double page spreads, would spill off screen on fit to height)
if you had a portrait orientated monitor, something that might happen often is fit to height would display the full image (and also have it spill off the sides since it only fits to height), whereas fit to container would keep the image inside the reading area