WebKit now supports the srcset attribute on image (img) elements (official specification from the W3C). This allows you, the developer, to specify higher-quality images for your users who have high-resolution displays, without penalizing the users who don’t. Importantly, it also provides a graceful fallback for browsers that don’t yet support the feature.

Too bad Google went and forked WebKit, otherwise Chrome would probably have support for this too.

(via Mr. Gruber)