What’s with the black top bar? Is Stack Exchange in mourning?

Sun, yardarm, so forth. pic.twitter.com/EHEpVm7fMS
@markrglover Old age. Next you’ll be standing there with the bulb in your hand in the middle of the room, wondering why you fetched it.
@charlie_cat_esq Sorry! But it didn’t take much of a trip for me to find some, you may well be lucky with random exploring.
@charlie_cat_esq No, Victoria Square in Clifton Village.
Halfmatt. @ The Galley instagram.com/p/him5j3JC-_/
@Malarkey Oop, sorry, I thought I’d checked to see if I’d missed the reply boat!
@Malarkey Less than or equal to.
Just back from Thea Gilmore gig in Bath. Lush. Just time to squeeze in a wee dram before bed, too. Night, all.