I have a site with articles on a two column layout, with the content on the left. Right now I have the ads (large rectangle) in the middle of the articles. The average article is 700-900 words. Would it be better for CTR to have the ads at the top of the article right under the article's title?
Top left will be best and you need it at the bottom as well because your articles are quite lengthy and will require the users to scroll down.