Sinister Svengalis have pulled the strings behind the scenes in a host of books, plays and films, but how does the dubious central character of a Victorian bestseller open a window on to the fears and anxieties of its own century and our own? Isabel Hilton talks to Daniel Pick, whose book Svengali's Web explores a history of fascination and prejudice. Plus the first of a week-long selection of arts sites on the internet.