If you <A HREF="http://news.bbc.co.uk/1/hi/technology/5034098.stm">take your Net safety seriously,</A> you will probably have antivirus and a firewall and perhaps even an anti-spam program to stop the malicious software and messages getting at your home PC. On your browser you may have a pop-up blocker that stops the irritating adverts imposing themselves between you and what you want to look at. But this does not cover all the possible ways that the bad guys are trying to catch you out. Increasingly the makers of adware, spyware and viruses are using ordinary-looking Web sites as launch pads for their malicious creations that try to compromise your Windows computer when you visit.