Is Safari 5.0 still supported? For Safari 5.1 is a major version so dropping support for 5.0 would be in line with what jQuery declares to support.

Besides, Safari 5.0 has a really minimal usage right now, aroung 0.54% according to StatCounter: http://gs.statcounter.com/#browser_version_partially_combined-ww-weekly-201312-201313-bar