According to Jakob Nielsen nobody looks at picture advertising online:
“We call this banner blindness — people won’t see ads at all,” said Nielsen. “Ads might as well not exist as far as users are concerned, except for search ads.”
Okay… so you read the link. Remember any ads??
Fortunately, search driven ads (i.e. Google Adwords) work just fine:
“We thought we’d find [paid search] box blindness the way we did banner blindness, but that’s not the case. Users are interested in search ads and actually look at them.”
In my own experience this is quite true. Both for me personally as I browse the web and also as a buyer of tens of thousands of dollars of online advertising. Search based advertising works well but must be watched carefully for efficiency. Image/banners ads, hardly work at all.