Just as adult movies helped drive the growth of video recorders so sex has helped fuel the growth of the Internet. Thanks to e-mail, anonymity and search engines, "adult" Web sites are booming. But gauging the size of this market is difficult, as David Kerr of the UK Net watchdog Internet Watch Foundation (IWF) testifies. "It's very nebulous -- like anything on the Internet. But what we do know is that commercial sex Web sites are very popular and are very good at drawing people via search engines." That porn magazines are still stacked on the news agent's top shelf is a bizarre pre-Internet era hang-up. Today, almost anyone can get a fix without ever leaving their home. The notion of a raincoat-clad man shiftily buying an adult magazine over the counter is well worn. A young, clean-cut, white-collar professional with a Pentium II PC is nearer the mark. Playboy -- possibly the most famous adult entertainment brand in the world -- has built up an expansive cyber enterprise with online magazines, Playboy TV, home video distribution, chat rooms, email, music and a cyber shopping mall all stamped with the famous bunny silhouette logo. Most recently, the company added financial information to its site -- marking the company's more highbrow online strategy. "It's big business, Sex has helped sell the Internet," said Stephen Balkam, president of Recreational Software Advisory Council (RSAC). The US-based ratings body has 105,000 global Web sites that have volunteered to be scrutinised and graded. RSAC uses software originally developed at Stanford University to rate games and has now been re-jigged for the Internet. If your Web sites shows passionate kissing, expect a level 1 rating. But explicit sexual acts or "sex crimes" -- as the council puts it -- will incur the maximum level 4 rating. Between 12,000 and 15,000 sites are explicit level 4 -- that's around 15 percent of rated sites -- according to Balkam. "You can put up pretty graphic material on the net providing [the participants] are adults over the age of 18. It's pretty open," he said. With the proliferation of sex on the Net, policing this medium is proving difficult and a political minefield. In the US, the battle between freedom-of-speech protagonists and the God-fearing, bible-belt community rages on. US Congress' latest attempt to criminalise obscene online material is being challenged by civil libertarians who claim it is damned under the First Amendement. The latter camp has for the time being succeeded in thwarting this controversial Child Online Protection Act (COPA) but the government is determined to see COPA become law. In the UK, it's more of a tussle than a battle between the freedom of speech and the anti-porn camp. The IWF, launched three years ago by Pipex chief Peter Dawe, is charged with policing the Net. Its job is to stamp out paedophilia and hardcore porn and it works with UK service provider trade bodies Internet Service Providers Association (ISPA) and the London Internet Exchange (LINX) to get undesirable content removed from the network. "We look for mainly child porn and hard core adult porn such as bestiality and torture. We act on reports of indecent material online," said Kerr. "Many ISPs see it as beneficial to work with us as it can protect them from prosecution," said Kerr. And as he stresses, with the more serious issue of child porn, Internet Watch is not really bothered about two consenting adults having cyber sex. Part II E-Commerce... while many are scratching their heads figuring out how to make money from the Net, porn sites are literally showing off their assets and raking it in. Take me to the Web of Porn Special