Madonna paid tribute to Michael Jackson on Saturday night in the same arena where he was to stage his comeback. A picture of a young Michael appeared on stage while Madonna was performing “Holiday.” then the impersonator came on, wearing a sequined jacket, white T-shirt, white glove and white socks and the music switched to “Wanna Be Starting Something.” the impersonator worked through Mike’s moves, including the moonwalk, but didn’t sing. After the number, Madonna told the crowd, “Let’s give it up for one of the greatest artists the world has ever known,” and the crowd roared its approval. An estimated crowd of 17,000, including the fashion designer Valentino, turned out for Madonna’s concert, the first of two this weekend in London on her “Sticky & Sweet” tour. In the last dance, Madonna and her dancers all donned jeweled gloves on their right hands in a simple tribute. Behind the stage some words from Jackson’s “Man in the Mirror” were flashed up briefly. “If you want to make the world a better place look inside yourself and make a change.”