hakimel/reveal.js — pull request #617 by rexxars (2013-09-21 20:30:10+00:00)
Title: Focus body on visibility change to ensure keyboard shortcuts work

- Adds a listener for the visibilitychange event, which is typically fired when the user switches back to the presentation from another tab (for example after following a link).
- Checks if the body is the active (focused) element. If not, it blurs the active element and focuses the body.

This seems to fix issue #577 in Firefox and IE.