"It really depends on what you're trying to do," says Margaret Holland, when asked about optimal ad placement. A senior account manager here at Yahoo! Publisher Network, Margaret helps publishers get the most out of the Network. "From a click-through standpoint, most publishers get the best results when they place a ‘leaderboard' above the fold between the top nav and their rich content."
But not everyone wants to be that up-front with their advertising. Some prefer to place their ads in less-obvious but still eye-catching places. Eye tracking studies have shown that people tend to look at the top-center or top-left of a site first, then track to the right and down the right side, slanting back up across the page to just below the upper-left corner and down the left side – all in an instant.
In general, Margaret has a found that the second most active placement in terms of click-throughs tends to be the right-hand rail or margin. "Skyscrapers" and vertical banners do well when placed next to the content in the main body.
Square and rectangle ads placed within the center column also do well, provided they are placed in context to the content. Ads placed below the fold tend to perform least well, although that isn't a hard-and-fast rule. If you have some useful functionality or eye-catching media near the footer, that may be a good place to put an extra ad unit. Bear in mind, however, that when pairing ads with media or images, it must be apparent to the user that the media is not a part of the ad. Placing images next to ad units can be construed at an "inducement to click," and goes against Yahoo! Publisher Network's Terms and Conditions.
"Each site is different, and each publisher has different goals," Margaret notes. "Publishers should experiment with different placement, layouts, Reporting Categories and Ad Targeting combinations to achieve the best outcome."