Apple today seeded a new Safari 8.0.3 beta for developers running OS X Yosemite, along with a Safari 7.1.3 beta for Mavericks and a Safari 6.2.3 beta for Mountain Lion



From MacRumors:

Registered Mac developers can download the new Safari builds through the Software Update mechanism in the Mac App Store or through the Mac Dev Center. In the release notes for the new betas, Apple asks developers to focus on features like Extensions, Password AutoFill, HTML5 video playback, notifications, and more.

  Apple Seeds Safari 8.0.3, 7.1.3, and 6.2.3 to Developers