Safari is smarter in OS X El Capitan with easier access to muting annoying audio while browsing, new pinned tabs and AirPlay enhancements.
In Safari you can pin tabs to the browser so your favorite websites and services are always handy and take up less space in the tab area. Even when you close the browser and re-open it they will come back. When you pin a tab it also stays up to date.
Another new feature allows you to quickly mute the audio in a tab, without hunting the tab down. On OS X Yosemite you must look for the tab and then click pause or mute on the video. In OS X 10.11 this control is in the menu bar.
Apple also makes it easier to share a web video by letting users AirPlay just the video instead their whole screen. We'll also see Force Touch capabilities on more websites as OS X 10.11 allows developers to deliver new Force Touch Interactivity inside Safari.