What dock and what old homepage? This sounds more like user change and Firefox doesn't have a actual home page that loads but a simple default page that isn't a homepage.

He's saying that the dock, a Mac term for the row of apps that appears at the bottom of the page, disappears and reappears when the mouse hovers at the bottom of the page. This "improvement" showed up after a Firefox update. Annoying as hell. He'd like the dock to stay visible all the time. So would I. How do you do that?