If you hover your mouse it says "Remembering September 11th".
"A black ribbon is a symbol of remembrance or mourning. Wearing or displaying a black ribbon has been used for POW/MIA remembrance, mourning tragedies, or as a political statement." From Wikipedia.
Seems pretty legit, they've not posted a Doodle, presumably because a "Doodle" implies Fun. What's "fun" about September 11th?