A responsive image polyfill

Officially endorsed by the RICG

An img with srcset and sizes attributes

sizes="(min-width: 40em) 80vw, 100vw"
srcset="examples/images/medium.jpg 375w, 
        examples/images/large.jpg 480w,
        examples/images/extralarge.jpg 768w" 

Here's how that renders in the browser. Feel free to resize to see it change.

A giant stone face at The Bayon temple in Angkor Thom, Cambodia