It somewhat depends on the blog design (layout) and theme structure or function.. and depends on the size or shape of the ad? Some people place an ad right at the top of first post in the content div. This works good on a majority of blogs but not all. Also, if is a long tall ad? The side bar would be better. The best thing to do is experiment with the ad by trying it in a few different spots to see what you like best. Boulder
ATF - on blog and on any other page ATF always brings highest ctr see full details http://forums.digitalpoint.com/showthread.php?t=228283 http://forums.digitalpoint.com/showthread.php?t=237454 http://forums.digitalpoint.com/showthread.php?t=178570
And not always in sidebar, header. You can play with ads, and then you will give more clicks i think.