Norton Internet Security

[urb]

As cd34 mentioned, try not to use the IAB standard banners...

Typical Sizes
468 x 60 IMU - (Full Banner)
234 x 60 IMU - (Half Banner)
88 x 31 IMU - (Micro Bar)
120 x 90 IMU - (Button)
120 x 60 IMU - (Button)
120 x 240 IMU - (Vertical Banner)
125 x 125 IMU - (Square)
250 x 250 IMU - (Square)
300 x 250 IMU - (Medium Rectangle)
240 x 400 IMU - (Vertical Rectangle)
336 x 280 IMU - (Large Rectangle)
180 x 150 IMU - (Rectangle)
728 x 90 IMU - (Leaderboard)
160 x 600 IMU - (Wide Skyscraper)
120 x 600 IMU - (Skyscraper)
300 x 600 IMU - (Half Page Ad)

Also, don't use the words "ad" or "banner" in anything (including phpadsnew). Do not actually name your banners "banner01.jpg" or "sitead.jpg"

I've tested versions of Norton and Zone Alarm with various set ups, links, settings and sizes of banner... and although the above is a good rule of thumb... the results seem to be random. As if Norton/ZoneAlarm are intentionally randomising what their rules are, so as to keep affiliate webmasters guessing.

The only sure thing for them targeting sizes is 468x60 and 120x60 which in all cases were affected by Norton and Zone Alarm.