As we delve further in this series of posts on Google AdSense ad sizes, we’ll explore the less used and alternate versions of Google AdSense banners. The AdSense 234 x 60 – Half Banner is found in the “Other – Horizontal” category, after the four main recommended sizes. While this ad unit is in the Delisted Standard Ad Unit sizes on the IAB Ad Unit Guidelines, it can be found as a recommended size in the Microsoft Advertising Standard Ad specs. I think the reason for the difference is that the IAB creates standards for agencies and other large advertisers, while AdSense and Microsoft Advertising also provide marketing channels for smaller businesses and publishers.
The 234×60 – Half Banner is very useful in side columns, especially near a navigation menu or under a larger square or rectangle ad unit. I have also seen it used in the footer of a website or blog.