The recent release of Safari 9.0 brought a great new feature: pinned tabs. These tabs are locked to the lefthand side of your tab bar and stay in place, even when you open a new window or relaunch the browser.
The default behavior is to display the first letter of the site’s name on a color from the site’s theme. If you work on a site with a strong branding element, you’ll want to customize the icon on the pinned tab.
A detailed look at how to create icons for Safari’s new pinned tabs. I’ll be giving this a try real soon.