Merge pull request #65 from primer/browser_support

Browser and platform support in About page

docs/about.md

@@ -11,6 +11,10 @@ Primer is GitHub's internal CSS framework. It includes basic global styling for
 
 Open-sourcing Primer means sharing and learning with the community. There's a lot we can improve upon in Primer, and help is always appreciated. While we don't currently plan on building this out as a competitor to other front-end frameworks, we will occasionally add, remove, or modify things.
 
+### Browser support
+
+Primer currently supports Internet Explorer 9+ and the latest two versions of Chrome, Safari, and Firefox on OS X and Windows. While not a responsive or mobile-focused project, Mobile Safari and Chrome for Android should render just fine. Support for Linux-based browsers is not strictly guaranteed, but accounted for whenever possible.
+
 ### Future updates
 
 See the [roadmap](/roadmap) for a rough outline on what's slated for future versions of Primer.