I barely ever notice advertising on websites, the sides of the web page generally holding information which is not very useful to me. The only sites I notice them on are ones which make it very difficult for me to find the information I am looking for (because it is surrounded by loads of adverts) and now I tend to ignore those sites.

I finally got annoyed with those flash adverts everywhere and hogging up my bandwidth so use AdBlock... but even before, just cos it's served in front of a person does not mean they have taken any notice of it.