Thoughts about “the most successful ad placement on your blog”
As I stated before you will probably get less clicks with image banners instead of text link banners. Because if a reader see a blinking colourful image he will immediately think that’s an “ugly ad” and won’t click on it. So if you must use image banners try to use non-animated image banners. Another good idea can be to use image banners that don’t look so square and boring.
I haven’t tried using a 120×240 ad. But I guess it will do well as well. But I would rather use a 180 x 150 ad if I wanted two different ads shown.
I believe this ad placement works best with a fixed width layout and not with a liquid layout. Read more about Fixed or liquid site design.
The size of the banner depends on how width your post text is. If you want to use a 250×250 (or something similar) banner you should have a large blog post width.
If you got any more questions please don’t hesitate to send them or post them here as a comment. 
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