Board Thread:Roblox Q&A/@comment-98.195.91.130-20130404233422/@comment-4812386-20130628050916

The black bar is the hint bar, where the text contained in hint objects in your game appears. That particular message comes from a script written a long time ago by Mark Langen (Stravant on ROBLOX, formerly xLEGOX; now a ROBLOX employee) for his track kit, which he later released.