CSS: 100% width or height while keeping aspect ratio?

Question

Currently, with STYLE, I can use width: 100% and auto on the height (or vice versa), but I still can\'t constrain the image into a specific positio

Answer 1

By setting the CSS max-width property to 100%, an image will fill the width of it's parenting element, but won’t render larger than it's actual size, thus preserving resolution.

Setting the height property to auto maintains the aspect ratio of the image, using this technique allows static height to be overridden and enables the image to flex proportionally in all directions.

img {
    max-width: 100%;
    height: auto;      
}