With six songs performed in the course of 29 minutes, Madonna turned in her second live concert in seven years yesterday at London's Brixton Academy, and set a Web ratings record in the process. Compared to the three million viewers Paul McCartney attracted for his concert in Liverpool last year, about nine million fans reportedly tuned in to catch Madonna's show live over the Microsoft Network. Various reports from around the U.S., however, noted that the Webcast, besides delivering Madonna, also delivered some technical glitches, including frequently frozen images. Such snags aside, Madonna, 42, nearly seemed ready to take audience requests during the gig, but that proved not to be. "Which song should I do?" she rhetorically asked the crowd before stating, "Fortunately, this is not a democracy, so we're going to do 'Holiday.' " She then broke into an updated version of her 1983 hit, during which she shimmied atop a vintage pickup truck. As for wardrobe, she sported a T-shirt with the name of her 3-month-old son, Rocco Ritchie, on the front. The reverse side read "Lola," which is what the Material Mom calls her 3-year-old daughter, Lourdes.