America revisited Sept. 11 in huge numbers Sunday night. On the eve of the sixth-month anniversary of the terrorist attacks, CBS's harrowing Robert De Niro-hosted documentary, 9/11, notched a whopping 23.9 rating and a 33 share based on preliminary Nielsen data. As a result, CBS handily won the night. Meanwhile, firefighters who watched the virtually uninterrupted special said it was an accurate and sensitive account of the tragedy.