How to get custom-sized Adsense units on your blog
Just recently, the Adsense team quietly rolled out custom-fit Adsense units which means, as you can guess, that you can create a custom height and width of your ad unit.
All you need to do is to create a new ad unit, and when you do, you will notice the site now has the custom option, just select that and you’re off to the races.
The pros of using custom-sized ads
The first pro is they will likely look better. Unless you designed your blog around the common ad sizes, there are probably places where you have ad units that just don’t quite fit as well as they could or you’d like. As a result, maybe they don’t look as nice as one that fits well.
Second, they will help fight ad blindness. Adsense units haven’t really changed their look in the past decade and so, almost everyone, including your grandma, can quickly identify them as ads and, consequently, will pay little attention to them. You now have the ability to break out of those old standard units and create a new size and shape that integrates nicely with your blog and may get more interaction from the readers.
The cons of using custom-sized ads
Your ads will almost exclusively be text ads. Since banner advertisers only create so many different sizes (300×250, 728×90, and 160×600 are the most common), you can bet you’ll see very few image ads in the 436×278 ad unit you created.
Because of the previous point, your earnings may suffer. Like everything, this is definitely worth testing to see if it legitimately hurts your earnings or not, but the Adsense folks do issue a warning that your earnings may drop when using these units.
I’ve used custom Adsense units as long as I’ve had access to them, and after testing on my site, I found no measurable earnings drop, and they fit better and looked better, so I’ve stuck with them.