Twitter cards make it possible for you to attach media experiences to Tweets that link to your content. Simply add a few lines of HTML to your webpages, and users who Tweet links to your content will have a “card” added to the Tweet that’s visible to all of their followers. [Source: Twitter Developer: Twitter Cards]
More details about Geolocation API Specification.
Add support for the CSS @font-face property. This property allows you to specify a true type font file that includes a specific font you want to use to render a web page.
More details about @font-face
Video and Audio
Include support for the <video> and <audio>elements. This beta includes support for the OGG Theora and OGG Vorbis formats on all platforms
Pushup is an effort to push the web forward by helping users upgrade their outdated browsers. Give your users a better web experience today by installing Pushup on your domain! A subtle upgrade link is shown when people visit your website using an outdated browser. They can click this link to visit the upgrade website for that browser, or choose to be reminded after a time you specify.