I've been using vertical ad layouts mostly. However, I've often wondered if horizontal layouts get noticed more and thus encourage more clicks. Has anyone ever tried both on the same site and have any observations they can share?
The most important thing is that your ads are above the fold meaning they are seen on the screen before you scroll down. But then it's something of a compromise. If it looks fine and doesn't detract from your content putting a horizontal ad across the top or near the top might be best. In may case I usually use a vertical ad with part of it showing above the fold. That is the least intrusive to my content while still being where it is noticed by my visitors.
I like to put the ads near links - but not to near. And also inbetween blocks of text or data that is the focus of the visitor. I used to have the vertical ads off to the right but got far fewer clicks. Sandwiching these ads inbetween focus items is the best.
I think you have a point there that though the vertical towers are the least intrusive visitors would tend to notice only the top 2 or 3 ads.
I've tried horizontal ads and they seem to cut off the flow of the articles and am wondering about using the rectangle blocks. I'd like to float them to the right of the first paragraph of the articles. My problem is that I don't know how to do that. On an image I'd just align="right" but I don't know how to align a java script. How could I do this either with CSS or with HTML?
I run the 5 ad skyscrapers on my site. I made a change over a week ago where I changed absolutely nothing with the ads other than to make bold color changes with the ads on each successive page of each of my site's topics.
Evidently this has the effect of drawing attention to them. Clicks are up easily 25%.