Apple is making strides to support web development with its release of the Safari Technology Preview. This is a browser made especially for developers, which lets them get a glimpse of future technologies in both OSX and iOS and play around with these technologies in websites and extensions. What sets the new browser apart is its handy standalone role. This means developers can run it side-by-side with the mainstream version of Safari, which makes workflows easier as it allows seamless switching...
The DOM has been a part of our webpages from the beginning, and since the earliest browsers there have always been certain things we wanted, but couldn’t get from the DOM; and other things we wanted to hide. The shadow DOM is designed exactly for that, it hides DOM subtrees under shadow roots, giving you a method of creating a better and more functional encapsulation in the DOM. Browser support ... This functionality is very much new and experimental so it’s only available at the moment in Chrome 25+...