That won't work right; it can overflow vertically. Consider the case of a 10x10 image in a container of width 500px and height 100px... Ideally you would want it to end up 100x100, but it will end up 500x500 with that CSS.
Nope. This determines how the image is rendered within the img element. The img element itself won’t be constrained in its aspect ratio. E.g. try adding a border or drop-shadow to the img and you’ll see the problem.
