Web site name registrar Network Solutions is blocking access to a site owned by a controversial Dutch politician known for his confrontational views about Islam and Muslim immigrants. The move by one of the largest companies in the domain registration business is notable, experts say, because it may be the first documented case of Internet pre-censorship by a major U.S.-based Web registrar. The site in question is fitnathemovie.com, which is registered by Dutch Party for Freedom leader Geert Wilders. Wilders has said that he planned to post a short film on the site designed to rally support for banning the Koran in Holland. Wilders has said that Islam’s holy scripture urges followers to commit violent acts. Network Solutions imposed its block on Wilders’s site Saturday evening, at which time it hosted little more than an image of the Koran on its homepage. But a company spokeswoman said Sunday evening that