Google AdSense now makes it possible for users to create custom ad sizes.
Custom sized ads perform just like the “traditional” standard size ads that show a text or display ad, depending on which is likely to have the best performance for the impression.
For text ads, they will determine the optimal number of text ads to display for a given impression, and show the ads the same way they appear inside standard sizes.
As far as display ads, their system will determine the appropriate size ad to fit into the space you select.
There are some restrictions in place for maximum and minimum pixels for ad sizes. Any custom ad size that falls outside of the restrictions won’t appear on a page.
When you want to give this a try, create an ad unit in the usual way, and then select “Custom ad size” from the Ad size drop-down and set the desired width and height for your ad unit in the process.
Then copy and paste the ad code into the HTML source code of your page where you’d like the ad to appear.
I can’t remember how many sites I’ve created over the years with layouts designed to accommodate Google AdSense sizes, so I am glad to see this.