mallyh, it means Norton Antivirus Protection software, which many people instal on their computers. It stops viruses, and other nasty things, getting in to your PC. If it detects an 'intruder' it flashes up a little message on your screen, and it seems that quite a lot of ABers are finding that their PCs are being targeted by a certain naughty website (ads.silverdisc.co.uk) that wants to infect their computers with something malicious.